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•AIR COMPRESSORS

AND

BLOWING ENGINES

SPECIALLY ADAPTED FOR ENGINEERS.

CHAS. H. INNES, M.A.,

Lecturer on Engineering at Rutherford College, Newcastle-on-Tyne ;

Author of "Problems in Machine Design," "Centrifugal Pumps, Turbines,
and Water Motors," "The Fan," &c.

1906.
THE TECHNICAL PUBLISHING CO. LIMITED,

287, DEANSGATE, MANCHESTER, AND 359, STRAND, LONDON;
D. VAN NOSTRAND Co., 23, Murray Street, and 27, Warren Street, New York ;

E. W. COLE, Sydney and Melbourne, Australia;;

GEO. ROBERTSON AND Co. PROPRIETARY LIMITED, Melbourne, Sydney, Adelaide,
and Brisbane ; and all Booksellers.

GENERAL

THIS BOOK IS DEDICATED

PEOPLE OF TYNESIDE,

WHOSE INTELLIGENT APPRECIATION OF SCIENTIFIC

KNOWLEDGE IS SO WELL KNOWN.

187724

PREFACE.

THE following work deals with the construction of Blowing Engines and
Air Compressors, and is reprinted from a series of articles which
originally appeared in The Practical Engineer. The first chapter
discusses the properties of air, and shows how to calculate the work
required for compression under various circumstances. The second
describes several experiments with compressors, and explains the
methods of calculating the various efficiencies. The third deals with
the theory of valves for equalisation of pressure, and the fourth is
devoted to the construction of Blowing Engines. Chapter V. com-
mences the description of Air Compressors. These have self-acting
valves, and the remainder of the book is devoted to those with
mechanically controlled valves.

I take this opportunity of thanking the many firms who have supplied
me with information concerning their machines.

C. H. INNES.

Rutherfoi-d College,

Newcastle-on-Tyne, August, 1906.

CONTENTS.

CHAPTER I. PAGK

Physical Properties of Air 1

CHAPTER II.
Experiments with Compressors 31

CHAPTER III.
Valves for Producing Equalisation of Pressure 39

CHAPTER IV.
Blowing Engines 44

CHAPTER V.
Air Compressors 123

CHAPTER VI
Air Compressors — continued 197

AIR COMPRESSORS

AND

BLOWING ENGINES

CHAPTER I.
PHYSICAL PKOPERTIES OF AIR.

1. Physical Properties of Air. — Air is a gas, and
therefore

U4=pv = R£ ..... (1)

where p is pressure in pounds per square inch, v is the
number of cubic feet per pound, or the specific volume t is
the absolute temperature ; so that

t = F + 460-6,
or = C + 273-7,

where F is its temperature in Fahrenheit and C in Centi-
grade degrees. If the former scale is used, R = 53 '2, and
if the latter, R = 95 8. When air is compressed or expands
isothermally, or at a constant temperature,

p v = constant . . . . . (2)

but when it is compressed or expands adiabatically — i.e.,
without gain or loss of heat,

p vy = constant ..... (3)
where y = I '408

2AC

2 AIR COMPRESSORS AND BLOWING ENGINES.

where K^ and KD are the capacities for heat expressed in
foot-pounds of a pound of air at constant pressure and
constant volume. Equation (3) is proved in most works on
the steam engine.* It is also important to remember that,
if a pound of gas changes its pressure and volume in any
manner,

H = W + Kr fe - tz)

where H is the heat taken in, W is the work done by the
gas, and t2, ^ are the initial and final temperatures. Hence,
if the gas is compressed, W is negative, and H is negative ;
so that if

W = - U0, and H = - H^

H = - U0 + K, (^ - tz)
or H! = U0 - K, (t, - t,) .... (4)

or Hj, the heat in foot-pounds given out by the gas, is the
difference between the work in foot-pounds oone upon it
and the internal heat in foot-pounds added to the gas.

2. Work Required to Compress Air. — Let FC, fig. 1,
represent a volume vz of air, and let E G represent v± the
volume to which it is compressed, the pressure changing
from £>2 at C to p^ at B, and the air being forced out into
a large reservoir, in which the pressure is kept constant.
Then, if we first assume isothermal compression between C
and B, the work done while the volume changes from v2 to
v is

U1=144/' pdv = Utf ^1= 144&hyp. log !i

= 144 p1 ?;x hyp. log £2 = 144 p» vz hyp. log £3 .
Pz Ps

The work done during the expulsion of the air is
U2

* " The Steam Engine," by Cotterill, Holmes, or Perry.

WORK REQUIRED TO COMPRESS AIR. 3

and that done ~by the atmospheric air upon the suction side
of the' compressing piston is

U3 = 144 p1v1 = 144 p2v2;
hence the total work done is

U = Ui + U2 - U3 - 144p2v2hyp.

(5)

The four quantities, Uj, U0, U3, U, are represented in
fig. 1 by the areas G B C D, GBAE, FCDE, andABCF.
Equation (5) shows us that, no matter what the temperature

FIG. l.

may be, to compress a given volume vz from pressure p^ to
Pi requires a fixed quantity of work. But if it is the weight
of air that must be considered, the matter is different ; then

U = R tz hyp. log £i per Ib (5a)

so that the lower the temperature the less U becomes. U is
the least quantity of work required to compress a given
volume v2 from p% to p^. Equation (4) shows us that the
heat given out is equal to the useful work done upon the
air for U = ^. Isothermal compression is, however, not the
rule, and is unattainable unless cooling water can be obtained
considerably colder than the atmosphere.

Let us next consider the case of compression when the
curve C B follows the law

p vn = L

4 AIR COMPRESSORS AND BLOWING ENGINES.

Then

V» V.,

TJ f 144 Z - 144 f'^dv _ 144 k f i-« _ i-«\

V, Vx

144

».- 1

U2 and U3 have the same values as before, so that

U = Uj. + U2 - U3 = 144^ (;>i^i - ^2v2). . (6)
or

per pound ; so that the work per pound decreases with the
initial temperature, but is fixed for given values of p^ jt?2,
and v2. If the compression is adiabatic, y must be sub-
stituted for n in equations (6), (6a), and (66).

Numerical Example. — To find the work required to
compress 1 cubic foot of atmospheric air of pressure 14*7 Ib.
per square inch to a pressure of 4 atmospheres absolute.

First, assuming isothermal compression,

p2 = 14-7,

v2 = 1,

Pz
From (5)

U = 144 pa v3 hyp. log^i = 144 x 14'7 hyp. log 4

= 2931 foot-pounda.

TOTAL AND VOLUMETKIC EFFICIENCIES. 5

Secondly, supposing that the compression is adiabatic,
from (6a),

ps -408

144 x 1-40814-7 x-495

This is 682 foot-pounds more than with isothermal
compression.

3. Total and Volumetric Efficiencies. — In any machine the
useful work done is less than that which must be done by
the agent, owing to friction and other losses. Thus, if U
is the useful work calculated from equation (5), and I is the
indicated work done in the same period by a steam engine
driving the compressor, then the total efficiency of air
compressor and steam engine is

But it is often convenient to be able to compare the
actual work done upon the air, as obtained by indicating the
air compressor cylinder, with the least quantity of work
ideally necessary to obtain the same final pressure with the
same quantity of air. This will be called the air efficiency*
and if U4 is the quantity of work for a given volume of
atmospheric air v2 obtained from the indicator diagram of the
air cylinders, then the air efficiency

1 44 px v2 hyp. log ^—

i* = - -fT- -^ ..... (8)

^4 >x

A compressor never delivers a quantity of air correspond-
ing to the volume swept out by the piston, because the
pressure in the cylinder at the end of the suction stroke is
usually a little less than that of the atmosphere, and also
because the air in the clearance must expand from pl to p2
before the suction valves can open. Let Q be the number
of cubic feet of air at atmospheric pressure actually taken in

* Also called the efficiency of compression.

AIR COMPRESSORS AND BLOWING ENGINES.

per minute, let A be the piston area in square inches for a
single-acting compressor, and let Au A2 be the areas on
either side for a double-acting compressor, while L and R
are the stroke in feet and revolutions per minute respec-
tively. Then the volumetric efficiency

ALR

for a single-acting compressor, and

(9)

! + AS) L R

for a double-acting compressor.

Numerical Examples. — (1) What is the air efficiency in
the numerical example of section 2, assuming adiabatic
compression, ^j ^jL ^

* = !?§ = ™»1 per cent, */•*/*

showing the necessity for cooling the air during compression
if a high efficiency is to be obtained.

Fio.

(2) What is the volumetric efficiency of a double-acting
compressor whose piston areas are 160 and 140 square
inches, with a stroke of 2 ft, making 100 revolutions per
minute, the actual volume of air delivered (reduced to
atmospheric pressure and temperature) being 333 cubic feet,

EFFECT OF CLEARANCE. 7

4. On the Effect of Clearance. — In section 2 we have
neglected cylinder clearance, and although this does not
affect equations (5) to (66) supposing v2 is the volume of
atmospheric air compressed, nor the value of rj2 in (8), it is
interesting to see how this is the ca&e. Let V2 be the
cylinder volume, or that swept out by the piston in one
stroke in cubic feet, and let c V2 be the volume • of the
clearance. In fig. 2 CL is the cylinder volume, FL the
clearance, while C B and A H are curves of compression and
expansion. The latter takes place during the commence-
ment of the return stroke, the air expanding from the
clearance, and the suction valves do not open until the
point H is reached, so that the volume v2 of air drawn in is
represented by C H. Since air does not accumulate in the
cylinder, it is clear that

for A H and B C follow the same law, pvn — constant, and
if HC in fig. 2 = FC in fig. 1, and HK and MN are at
the same height in figs. 1 and 2 respectively, then H K =
MN, so that the area ABC F in fig. 1 = area ABCH in
fig. 2, and as these are the indicator diagrams in the two
cases, the work done in each case is the same for a given
exponent n. Let us first suppose isothermal compression ;
then, reasoning as in section 2, the work represented by the
area

KBCF = 144p2V2(l + c)hyp. log^-1
and since

FH = cVo^1
ft

K A H F = 144^2 c V2^l hyp. log & = 144 ^ c V2 hyp. log £

so that

U = ABCH = 144V2{p2(l + c) - ft c} hyp. log^.

8 AIR COMPRESSORS AND BLOWING ENGINES.

the useful work done per stroke, which it will be noticed
becomes zero when

that is, when B and A coincide.
The volumetric efficiency is

so that as the pressure increases the atmospheric air dis-
charged per stroke becomes less.

If the exponent n is greater than unity,

KBCF = ili?Ljo2V2(l + c)( (^V^-l I
n - I ( \pz)

V A TJ T? IT 4^ n -rj- /^l\~ I /'Pl\ — 1 (

Jv A ±1. r = p.2 \ 2C\ I i II w ~ (

so that

U = ABCH = p.

?t - 1

+ c-o . . . (12)

which becomes zero when

1 + c

c
and the volumetric efficiency

-es. . . . (13)

Numerical Example. — The cylinder volume is 1 cubic
foot, the clearance is one-fifth of the cylinder volume, and
the compression is to 4 atmospheres ; to find the work per
stroke, and the volumetric efficiency. First assuming
isothermal compression, and using equation (10),

U = 144 x 14-7 {1J - *} hyp. log 4
= 144 x 14-7 x | x 2-3 x -6021
= 1172 foot-pounds.

EFFECT OF CLEARANCE. 9

exactly two-fifths of what it was in section 2. The volu-
metric efficiency from (11) is

% = | = 40 per cent.

Next assuming adiabatic compression, with n = 1-408,
using (12),

_ 144 x 14-7 x -495 x 3-324
•29 x 5

= 2402ft.-lbs.
The volumetric efficiency from (13) is

T] -.= U - 4- x 4'71 = 66-48 per cent.

In both of these cases it is evident that an increase in the
volumetric efficiency would be an advantage, even if it were
obtained with some slight loss of air efficiency, for we must

consider losses by friction, and weight per horse power, in
fixing the dimensions of any machine. If the size of a
machine is excessive in proportion to power, the mechanical
efficiency will be low, owing to friction, although the air
efficiency may be high, and the cost will be greater ; so that
a small machine with a comparatively low air efficiency may
be better in every way than a larger one in which it is
higher.

10 AIR COMPEESSOKS AND BLOWING ENGINES.

5. Equalisation of Pressure on both Sides of the Piston at
the End of the Stroke. — The reduction of volumetric efficiency
being due to the expansion of the compressed air in the
clearance space, if some of this compressed air is transferred
to the other side of the piston, where compression is com-
mencing, there will be a considerable increase in the
volumetric efficiency, in tig. 3 AM is tke clearance volume
cV2, and the air in this, at a pressure plt is put in communi-
cation with the air at the other side, whose pressure is jt?2
and volume (1 + c) V2. To be strictly accurate, we should
also take into account the volume of the equalisation valve ;
but this is comparatively small, and may be neglected. The
pressure then becomes ps, as shown at L and C, and admission
commences when the expansion curve L H is completed — i.e.,
at the point H of the stroke when the pressure has fallen to
p2. The volumetric efficiency is

and is evidently greater than that in fig. 2. Assuming,
first, that compression, equalisation, and expansion are
isothermal,

TV-' + M! + c) = p3 (I + 2c)

so that if N is the number of atmospheres to which the air
is compressed,

1 + (1 + N)c

GH = cVt* = cVo +°

pz 1 -f 2c

and

GD - HG . 1 + (1 + N)c

= ~

^ ^

Next let us suppose that compression, etc., take place
adiabatically ; then, during equalisation of pressure, the

EQUALISATION OF PRESSURE- 11

intrinsic energy of the two quantities of air that mix
remains unchanged. Now, the intrinsic energy of a pound
of air is Kv t where t is its absolute temperature, and Kv its
capacity for heat at constant volume ; hence, if V and p are
volume and pressure of any weight of gas, its intrinsic
energy

T J°VK

TTKv'

Therefore

2c) Kv ' ftcVaK,' KM1 + c)Kv

K K R

PsV2(l + 2c) «.ftcV, + p2V2(l + c)

or p3 has the same value as in (14).
But L H is now an adiabatic, and

Numerical Example. — To calculate p3 and rjs for a cylinder
volume of 1 cubic foot, a clearance of one-fifth of a cubic
foot, and compression to four atmospheres.

In any case, from (14),

For isothermal compression, from (15),

% = 1 - 5JLEE = g = 914 per cent.
With adiabatic compression, from (16),

fc = If - * | 1 +15,X-^ } V - 94-3 per cent

12 AIR COMPRESSORS AND BLOWING ENGINES.

6. Work Done per Stroke ivith Equalisation of Pressure. —
This is represented by the area A B C D H L, and

ABCDHL = MBCK + KCDG-KLAM-KLHG.

First, assuming isothermal compression, the above

= U = 144 V2 \ (1 + c) fehyp. log^1 + P3 - Pz)

- (l\-Ps) c - Ps c hyp. log £? | . . (17)

Using (14), the above may be put in terms of pt and p2,
pz being eliminated, but it is then very complicated, and
we prefer to leave it in the above form.

If the compression is adiabatic, we get

Numerical Example. — To find the work required per
stroke when the cylinder volume is 1 cubic foot, the clear-
ance one-fifth of a cubic foot, and the compression to four
atmospheres.

First, assuming isothermal compression from (17) and (14),

{KO.O
H x (21 hyp. log ^2 + 6-3) - 37-8 x i

- v hyp- log f^ }

= 144 {1^(21-6 + 6-3) - 7-56 - 1-5}
= 3860 foot-pounds.

The volumetric efficiency has been shown to be 91 '4 per
cent, so that the air efficiency

2931 x91-4
%= -3860- =69'5 P

KISE OF TEMPERATURE DURING COMPRESSION. 13

The low efficiency is, of course, due to the somewhat large
clearance.

With adiabatic compression, from (18),

U-H4 1-23-45x21

{1-2(3-

37'8 3-45 x 14-7 / 21

5 5

= 4500 f ot-pounds.
The air efficiency is here

2931 x -943

4500

6T5 per cent,

so that our statement above, that increased volumetric
efficiency produces a loss of air efficiency, is corroborated.

7. Rise of Temperature during Compression and the
Quantity of Heat that must be Withdrawn. — Let pvn —
constant be the equation of the compression curve, n being,
of course, greater than unity and less than y. Then, since

subscript 2 referring to the commencement, and 1 to the
end of the compression curve, such as C B, fig. 1,

and equation (4) gives us per pound

Hx = U0 - K, ft - Q . . . (4)
Here U0 is the work done during compression = G B C D,

fig- 1 J

- TT 144 (pl vl - p2 v2)

n - 1

K ft -

perlb.

so that HJ = 144 AR\"_y { R - K, (» - 1) }• . (19)

14 AIR COMPRESSORS AND BLOWING ENGINES.

when the volume is known, or

HI -'B-K. (»-!) • (2°)

per pound of air, R = 53 '2, and Kv = 130-15 foot-pounds.
Equation (19) may also be put in the form

H^144H{g)^-1}iR"KKM"1-i- ^

It may be mentioned here that where air is used to burn
fuel the weight is the quantity that should be known, but
when used for transmission of power, the volume.

With equalisation of pressure at the end of the stroke, the
quantity of heat that must be? withdrawn is given by (21)
if ps is substituted for f2.

Numerical JSxample. — The clearance volume is one-fifth
of a cubic foot, and that of the cylinder 1 cubic foot ; the
compression is four atmospheres, and the exponent n is 1*25.
To find Hj in foot-pounds per stroke.

Here v2 = V2 (1 + c) = 1'2 cubic feet, so that
H, = 144 x U'7;51"2{4-' - 1 } { 53-2- 130-15 x -25 |

= 1265 foot-pounds.
The temperature ^ absolute at the end of compression is

^ = fa /^\±~ « 521 x 4- = 686 absolute
= 225 Fah.

if the temperature of the atmosphere is 60 Fah.
Had the compression been adiabatic, then

^ = ft/£y^ = 521 x429 = 775 absolute

= 314 Fah.

In order to find the highest temperature from an actual
diagram equation (1) may be used, because we know the

RISE OF TEMPERATURE DURING COMPRESSION. 15

volumes and pressures of the admitted and discharged air
whether there be equalisation of pressure or no. Let vz be
the volume of air admitted per stroke, which is F C, H C, or
H D in figs. 1, 2, and 3 respectively, and if vl is the volume
of air discharged, it is represented by A B in all three figures.
In an actual diagram p4, the actual terminal pressure of the
suction stroke will be a trifle less than p2, but of course it
can be obtained by measurement from the diagram. The
temperature of the atmosphere is #2, so that

Pi Vl

3- or fx
?>4*>a

(21)

Strictly speaking, ^ is not the highest temperature,
because PI is not the highest pressure. In fig. 4, which is
an indicator diagram from an air compressor constructed by

\ \
\

Cylinder, Sin. bore; 12 in. stroke; revolutions, 140 per minute ; I.H.P , 14'7,
neglecting friction ; air delivered, 93'5 per cent of cylinder capacity ; clearance,
1-081 per cent; mechanical efficiency, neglecting friction,

SO per cent.

FIG. 4.

the Tilghmau's Patent Sand Blast Co., it will be noticed
that the pressure at the end of compression is higher than
that at the end of discharge, which latter, of course, is equal
to PU and it is the former, p5) which must be used in (21) ;
also the volume vs at this pressure is really less than v , and
can only be found approximately by producing the curve of
expansion from the clearance upwards. Then the horizontal

16 AIR COMPRESSORS AND BLOWING ENGINES.

line between the curves of expansion and compression at a
height corresponding to ps will give vS9 so that the highest
temperature

in place ot vlt v2, and VB, the corresponding lengths on the
diagram in inches, would be used.

Numerical Example. — In fig. 4 the horizontal distance
between the lower end of the expansion curve and the foot
of the compression curve is 11 centimetres. This is v2, and
v6 is 2*35 centimetres. The pressure ;:>4 at the end of the
suction stroke is 14 Ib. per square inch, while the highest
pressure on the compression curve is 94 -5. Assuming an
atmospheric temperature of 60 deg. Fah., then the highest
temperature from (22) is

521 x 94-5 x 2-35 7Kn
ts — - — — - = 750 absolute
14 x 11

= 289 Fah.

If the compression had been adiabatic, the temperature
would have been

tB = ;2(TA^= 521 x 6-76<M= 906 absolute
\pj

= 445 Fah.

8. Cooling of the Air. — Equation (66) shows that it is
advantageous to cool the air during admission when the
weight of air supplied, and not its volume, is considered, for
the work per pound is shown to be proportional to /2, which
may, in practice, be taken as the temperature at the end
of admission. But (6a) shows that for a given volume of
atmospheric air cooling during admission is useless. If the
air is to be used for driving machinery at a distance, cooling
during the discharge is useless, because it does not decrease
the work 144 (p^ — p^) v^ which is required to expel the air,
and the air will be cooled in the pipes during transmission.
If the air is to be used at once, to cool it during discharge
is wasteful, because it thereby loses some of its intrinsic

THE EXPONENT OF THE COMPRESSION CURVE. 17

energy. It is therefore clear that cooling should take place
during compression, and cease as soon as discharge com-
mences. The object, of course, is to reduce n as near to
unity as possible. Much cooling cannot be done during
admission unless water much colder than the air can be
obtained. In spite of this there are many examples of
compressors in which water is injected during the suction
stroke.

9. To Find ike Exponent of the Compression Curve. —
If p vn = constant,

log PJ_ + n log «>! = log p.2 + n log vz.

Hence, on the ideal diagram in which the compression curve
lies between p} and ;).2,

n log ft -log ft (23)

log v2 - log Vl

v1 and v2 being the final and initial volumes ; so that in fig. 1

v.2 = v2 and v1 = v^
In figs. 2 and 3,

v2 = Vj (1 + c) and vl = Vx -I- c T2 ;

so that unless we know c we cannot use (23). If, howevei,
we assume that the whole compression curve follows the
above law, then, if we cannot actually measure the clearance
volume, we can calculate it and also w, with the result that
V V V 2

• — Vl V2 V«

n can now be calculated from (23).

Numerical Example. — As in the previous example, the
pressures at the commencement and end of compression are
14 and 9 4 '5 Ib. respectively, while the volumes Vx and V?
(neglecting clearance) are represented by 2 '35 and ll'6
centimetres; p6 = J p\p-2 = 36 '3 absolute, and V6 = 5 *35
centimetres ; to calculate n and the clearance as a fraction
of the cylinder volume,

Vi V2 ~ Ve* = 2'35 x 11'8 - 5-35 *

= V2 (2 V6 - Vi - V2) 11-8 (10-7 - 14-15)

* Vfl is the value of V when pa
'3AC

AIR COMPRESSORS AND BLOWING ENGINES,

= 0'965 per cent, and c VD is represented by '11 centimetre^
It is given in fig, 4 as l'08l per cent.

log 94-5 - log U _ r21
log 11-91 - log 2-46 ~

It is not advisable, however, to trust to the calculated
value of c, as the equation to the curve is not always p vn =
constant.

10. Compound Air Compressors. — In order to reduce the
amount of work and the stresses upon the working parts,
compression is effected in two or more stages, the air being
cooled in receivers placed between the cylinders. Fig. 5 is
a combined diagram of compound compression, neglecting

6 C D

FIG. 5.

clearance ; A C F E is the diagram of the high-pressure
cylinder, and E G K H that of the low ; K F B is an isother-
mal, and K G D a curve whose equation is p vn = constant,
which we shall suppose is the compression curve in a single
cylinder compressing to the same pressure. The air is dis-
charged from the low-pressure cylinder with a volume E G
into a large receiver, where we suppose its pressure to remain
constant while it is cooled to the volume E F at atmospheric
temperature. The high-pressure cylinder now draws in this
volume and compresses it to the pressure required and the

-COMPOUND AIR COMPRESSORS. 19

volume A C. The actual work required is thus represented
by the areas ACFE and EGKH; the quantity that
would have to be done in a single cylinder is K D A H, so
that the work C D G F is saved. The ideal amount of work
needed is A B K H. Let plt v^ be the pressure and volume
at C, p3, vs those at F, and p^ v2 those at K ; we shall first
find the ratio of E F to H K, that will make the work that
is to be done a minimum.

. (6a)

but ps vs = pz Vfy as F K is an isothermal ; therefore the
total work done

U - 1M-* ft v, [(*)¥ + (*)¥ - 2] . (25)
n — 1 LV2V VP37

so that (— \~n~ + ( — )~ must be a minimum.

\Pa/ W

Let p~ = P,

P P

then u = — + — - must be a minimum.

Pa PS

Differentiating u with respect to P3 and equating to 0, we
get

du 1 PI _ n

TF3 ~ P2 " P? ~
.-. P32 = PI P2

or ?V = 2hP*

Let the isothermal B K be p v = c. Then

' £1 = PL f!

^3" P* v?

or vs = v2 /P* (26)

20 AIR COMPRESSORS AND BLOWING ENGINES.

or if d, D are the diameters of the high-pressure and low-
pressure cylinders, both of the same stroke,

Equation (25) now becomes

U — n i}., vS CP£\*n — ll

» — 1 "LV^2/ J

If there are several cylinders, as in fig. 6, and if the
intermediate pressures at C and F are ps, p± respectively,
then, as we have shown,

so that pi, /?3, £>4, and p.2 are in geometrical progression. Let
^s> V4n V2 be the volumes of the cylinders CD, F G, and K L,
and let A M be VQ. Let

and therefore

— - r

then

or K - V7

therefore v2 .—

COMPOUND AIE COMPRESSORS.

and if the diameter of the high-pressure cylinder is dS) and
that of the intermediate </4, then

(29)

Numerical Example. — A compound air compressor has a
low-pressure cylinder whose diameter is 24 in., the strokes
of both high and low pressure pistons are 2 ft., and the
number of revolutions per minute is 140. The air is
compressed to 7 atmospheres. Assuming that n = 1'25,
neglecting clearance, and assuming a volumetric efficiency
of 95 per cent, to find the diameter of the high-pressure
cylinder and the horse power.

FIG.

The diameter of the high-pressure cylinder is

<73 = 24 x -i 147 in.

v 7

and

Pz =

= 38-81b.

The work per stroke, with '95 volumetric efficiency, is given
by ('28).

U = — x 14-7 x JLx 242 x
•25 4

= 27000 foot-pounds.

2 [7^ - ll

x 2 x -95

22 AIR COMPRESSORS AND BLOWING ENGINES.

27000 x 280

Ihe horse power = • — = 229.

33000

Of course the indicated horse power of the steam cylinders
is more than this, as friction has to be overcome.

The ratio of the work done, neglecting clearance, in a
compound compressor to that in a simple compressor can be
obtained from (28) and (6a). Dividing the former by the
latter, we obtain

- 1.

+ 1 . . . (30)

In the above example this is

R =

2-214

The improved volumetric efficiency of a compound com-
pressor is evident. For example, if we assume a clearance
of ^ the volumetric efficiency for a simple compressor
would be, from (13),

- c= 1-05 - 7

= 1-050 - -237 ^ -813.

In the compound air compressor the highest pressure in
the low-pressure cylinder is pzj7, because the compression
is to 7 atmospheres ; hence

= 1-05 - 7x = '94L

Numerical Example.— Pa? is to be compressed to 200
atmospheres in three stages. To find the work required per

COMPOUND AIR COMPRESSORS. 23

cubic foot of atmospheric air, supposing the compression in
each cylinder is adiabatic. Also to find the horse power and
diameters of cylinders, if that of the low-pressure cylinder
is 25 in., the stroke 30 in., and revolutions per minute 90,
the volumetric efficiency being 85 per cent.

= 5-848

The formula for the work required is obtained in the same
way as (28), and is

U = 3 x 144 _^_ PzvA (£)~- 1 1 . (31)
n — 1 I ^Pv

and if n — y, this becomes, if v.2 = 1 cubic foot,

U = 3 x 144 x 3-44 x 147 j 5-848^ - 1 |

= 14800 foot-pounds.
The number of cubic feet of atmospheric air per minute is

so that the horse power required, exclusive of that needed to
overcome friction, is

HP - 148QQ * 13°° - K«9

330UO

And as each cylinder requires the same amount of power,
the horse power of each will be 194.

AIR COMPRESSORS AND BLOWING ENGINES.

In this case the ratio of the work actually done to that
which would be required in a simple engine is

7-1

3 J ('^ 37

R =

7-1

(I) 7 - '

(32)

3 ( 5-848 '29 - 1} _ ,«q
200 '29 - 1

11. Ratios of Cylinders, taking Clearance into Account. —
When clearance is taken into account the volume compressed
in any cylinder is H C, fig. '2, and

1 + c

-ten

Fig. 7 is the combined diagram of a three-stage air
compressor, and the volumes A B, C D, E F correspond to

G . ri

FIG. 7.

H C in fig. 2. In one revolution no work is done on the air
that is compressed into the clearance space and expands
again ; in fact, the work done in each of the three cylinders
is the same as that which would be done in cylinders without
clearance and having volumes A B, CD, E F. If we give
these volumes the same ratios as in section 10, we shall have
the most economical cylinder ratios. Let the pressures at

COMPOUND AIR COMPRESSORS. 25

A B and C D be />3 and p±, and the cylinder volumes of the
high-pressure and intermediate cylinders V3 and V4. Let
the clearance ratios be c3, c4, and c2. As in section 10, p^
Psi P4> an(l Pz are nl geometrical progression, and therefore

and

EF CD AB

Supposing all three pistons have the same stroke,

• • • (33)

and / i

,Er/t + «b-*(*yis

*.*&/ - W_ . . . (34)

The following table* gives the horse powrer required to
compress 1 cubic foot per minute, both isothermally and

* Air Compressor Catalogue of the Worthington Pump Company.

xf^^^SSv

/ y ~ r- -T- LJ C

AIR COMPRESSORS AND BLOWING ENGINES.

Isothermal
com-
pression.

Adiabatic
compression.

Two-stage
compression.

Three-stage
compression.

£
1

Atmospheres.

H.P. required to
mpress 1 cubic foot
per minute.

H.P. required to
mpress 1 cubic foot
ee air per minute.

Efficiency as
compared to
isothermal.

'inal temperature,
egrrees Fahrenheit.

H.P. required to
mpress 1 cubic foot
~ee air per minute.

33-

£-gs

inal temperature,
egrees Fahrenheit,
irmal inter-cooling.

H.P. required to
mpress 1 cubic foot
ee air per minute.

Efficiency as
compared to
isothermal.

inal temperature.
?grees Fahrenheit,
irmal inter-cooling.

8 *IH

0*4

'^fc

8"**

*afc

1-34

•0188

•0197

•96

106

1-6S

•0333

•0361

•93 •

145

2-02

•0481

•0505

•90

178

2-36

•0551

•063

•88

207

2-70

•0637

•075

•85

234

3-04

•0713

•085

•84

252

3-38

•0781

•095

•82

281

3'72

•0843

•104

•81

302

406

•0900

•112

•80

321

4-40

•0945

•120

•79

339

•109

•87

188

4-74

•0995

•128

'78

357

•115

•87

196

5-08

•1037

•134

•77

375

•121

•86

203

5-42

•1080

•141

•76

389

•120

•86

2U9

5*76

•1120

•148

•75

405

•131

•85

214^

— v

6-10

•1160

•154

•75

420

•136

•85

219

6-44

•1196

•160

•74

482

•141

•t5

224

6'78

•1230

•166

•74

441

•146

•84

229

7-12

•1260

•171

•74

459

•150

•84

234

7'46

•1290

•176

•73

472

•154

•84

239

100

7-80

•1320

•182

•73

485

•158

•83

243

110

8-48

•1371

•192

'72

501

•165

•83

250

120

9-16

•1422

•202

•71

529

•172

•83

257

130

9-84

•1467

•210

•70

560

•179

•82

2^5

140

10-52

•1510

•218

•69

570

•186

•82

272

150

11-20

•1547

•226

•69

589

•193

•81

279

•182

•85

200

160

11-88

•1583

•234

•68

607

•198

•si

285

•187

•85

204

170

12-56

•1622

•242

•67

624

•203

•80

291

•192

•85

207

180

13-24

•1656

•249

•67

640

•208

•80

297

•197

•84

211

190

13-92

•1687

•256

•66

657

•213

•79

303

•202

•84

214

200

14-6

•1720

•263

•65

672

•217

•79

309

•206

•83

218

22.^

16-4

•1790

•273

•64

715

•227

•79

320

215

•83

224

250

•1860

•2P2

•64

749

•237

•78

331

224

•83

230

275

19-7

•1920

•306

•63

780

•247

•78

342

•233

•82

230-

300

21-4

•1970

•317

•62

815

•256

•77

352

•241

•82

241

325

23-1

•2020

•328

•61

837

•264

•77

361

•247

•82

246

350

24 -8

•2060

•342

•60

867

•272

•76

370

•252

•82

250

375

26-5

•2100

•354

•59

892

•277

•76

375

•257

•82

254

400

27-2

•2140

•364

'59

915

•283

•76

380

•262

•82

258

450

317

•2230

•381

•58

960

295

•75

397

•272

•82

266

500

•2290

•39S

.'57

1001

•307

•75

413

•282

•81

274

LOSS OF PRESSURE IN PIPES. 27

adiabatically, in one, two, and three stages, with the efficiency
in the latter case compared with isothermal compression, and
the final temperature reached. For example, with 100 Ib.
gauge pressure the efficiency in single-stage compression is
73 per cent, and in two-stage 83, while the temperatures are
485 Fah. and 243 Fah.

12. On the Loss of Pressure during Transmission in a
Straight Pipe of Uniform Diameter. — Let Vx be the velocity
with which the air enters the pipe, and V2 that of discharge.
Let L be the total length, and D the diameter of the pipe,
both in feet. Let the pressures at A, B, C, D be p^ pz, p,
and p + dp in pounds per square inch; dp is of course a

|A CJ JD

i
i

1 ' '

Fio. 8.

negative quantity. Let the specific volumes at the same
points be vlt vz, v, and v •*• d v, and the velocities at C and
D be V and V + d V. The loss of head — i.e., of energy in
foot-pounds per pound of air — due to friction for a small
length dl of the pipe between C and D, fig. tf, is

,4dJ V2

h = f~w~ 27

In " The Development and Transmission of Power," Pro-
fessor Unwin gives

= -0027

h = kdl —
so that 2 g

7 "0108 /-i . 3 \ /Q^\

where , "DT~V + 10DJ ' * ' -

28 AIR COMPRESSORS AND BLOWING ENGINES

Let p be the density of the air at C, then

V VI

V p = - = constant = — - = - - .
v vt m

Since the velocity of flow increases, the increased kinetic
energy must be due to the work done by the air as it
expands from a volume v to v + dv, and this work has also
to overcome friction. The equation of energy is therefore

but --.

Letl44p = P, the pressure per square foot. Then we
may either suppose the expansion to take place isothermally
or according to the law p vn = constant. Assuming the
former, let P v = b. Then

which reduces to

ilog . (3o)

If we suppose the flow adiabatic, then

P vy = c or P = —

LOSS OF PRESSURE IN PIPES. 29

and the equation of energy becomes

cdv _ V d V kdlV2
~^T" ~J~ -27"

2<2V

- ~~

7+i

7+ i j 9

- P2— - ± hyp. log £L
»

(y + D«7' 7

^ - ft» 1 - 1-42 hyp. log ft . . (36)

Numerical Example. — A pipe is 1,000 ft. long, and air
enters it at a pressure of 100 Ib. per square inch, and is
discharged at 90 Ib. Its velocity at inflow is 80 ft. per
second ; >vhat must the diameter of the pipe be ?

First let us assume a temperature of 60 deg. Fah., or 521
absolute.

Pv = IU = b = 53-2 x 521 = 27700
and since

_ri = 1>92 = J_
Vx 80 = 41-6

so that (35) becomes

= 26-2 nearly.

'60 AIR COMPRESSORS AND BLOWING ENGINES.

Calling x = — , we have the quadratic,
JLa-s + x - 2-425 = 0

x = ?2 and D = "62ft. = 7 '42 in.
6

If we assume adiabatic expansion, and that the air enters
the pipe with a temperature of 750 absolute Fah., then

Rj = 53-2 x 750 = 9.7?
P " 14400

= 14400 x 2-771408
i_

60400, .'. c^ --- 2512, and (35) gives us

k = -0183; D = -81ft. = 972 in.
The loss of head at a bend is

where C is the mean radius of the bend and <£ the angle of
bend in degrees ; so that the equivalent length of straight
pipe is

EXPERIMENTS WITH COMPRESSORS. 31

CHAPTER II.
EXPERIMENTS WITH COMPRESSORS.

12#. Experiments with Compressors. — Test of a Reumaux
Compressor wit/i Mechanically - controlled Valves.* — This
engine had two steam and two compressing cylinders. The
diameter of the former was 700 mm. (27*6 in.), and of the
latter 620 mm. (24'4 in.), the stroke being 1,600 mm. (63 in.).
Experiments were made at 19, 26, 40, and 54 revolutions
per minute, the results of which, converted into British units,
are given in the following table : —

Revolutions per minute 19 26 40 54

Indicated horse power of steam cylinders . . 206 285 481 671
Indicated horse power of compressing

cylinders 183 254 386 525

Mechanical efficiency per cent 88'7 88'8 S0'3 78'3

Piston speed in feet per minute 198'5 273'5 420 566

In the third experiment the steam and air pressures were
S5'21b. by gauge, or 99 '9 absolute. The piston area is
2,941 square centimetres (456 square inches) on both sides
as the piston rod passes right through the compressing
cylinder, so that the piston displacement in cubic feet per
minute —

Vo = — x 420 = 1327 per cylinder.
144

The suction pressure is slightly below that of the atmo-
sphere, and the air expands from the clearance before fresh air
is admitted, so that the volumetric efficiency is 94 per cent.
This enables us to calculate the ideal horse power.

2 x -94 x 144 p2 V2 hyp. log —

TT «

33000

99-9
2 x -94 x 144 x 14-7 x 1327 x 2-3 log rj-^

« . iZ-i = 307.

33000

Portefeuille economique d. mach., vol. xii., pages 83 and 84.

2 AIR COMPRESSORS AND BLOWING ENGINES.

The total efficiency is therefore
307

64 per cent,
on is
= 7 9 '5 per cent.

and the efficiency of compression is

y]2 — ''
080

In this compressor water was sprayed into the cylinder.
The efficiency of compression with adiabatic compression is
74 per cent, so that the spray had some slight effect.

Tests of a Straad Compressor with Mechanically-controlled
Valves* — The leading dimensions of this engine were : —

Diameter of high-pressure steam cylinder .............. 550 mm. (21 7 in.)

Diameter of low-pressure steam cylinder .............. 800 mm. (81 '55 in.)

Diameter of high-pressure air cylinder ................ 400 mm. (1575 in.)

Diameter of low-pressure air cylinder .................. 650 mm. (25'6 in.)

Stroke ................................................ 1000 mm. (39'4 in.)

Steam pressure by gauge .............................. 118 Ib.

Mean revolutions per minute .......................... 50

Maximum revolutions per minute ...................... 75

Normal air pressure absolute .......................... 7 atmospheres.

Maximum air pressure absolute ........................ 9 atmospheres.

The experiments were carried out by Professor Schroter
and Gutermuth during the commencement of 1892, at the
Offenbach Power Station. The results are given by them in
the following table. We have added the total efficiency and
the air efficiency.

Barometer in atmospheres .......... 1'03 1'02 T02 1'02

Intermediate reservoir in atmospheres 2'88 2'82 2'90 277

Pressure pipes in atmospheres ...... 7 '12 7'10 8'62 7'10

Temperatures in degrees Cen. in

suction pipes ...................... 6 5'2 3"2 14'9

mgh-pressure pip. ...... - J"

Volumetric efficiency
L.P. air cylinder ...

Chevaux vapeur* in air cylinders.... 162-45 162-16 18078 232-88

Revolutionc per minute 50 50'1 507 707

Steam pressure by gauge 106-5 107 105*6 104*1

I. H. P. of steam cylinders 197'24 195-34 213-66 275*24

Feed water in pounds per H.P. hour 1575 17'05 16'00 16'80

Jacket drain in percent of feed water 9'6 12-3 12-0 10'6

Mechanical efficiency, per cent .. .. 82-4 83 84-6 84-6

•975 -974 -973 '974

•967 -970 -966 '965

•971 -972 -969 '969

].120 1,122 1,133 1,580

72-6 73-4 74-4 73'25

88 SS-5 88 86-6

Cubic feet of free air per minute

Total efficiency ^ per cent

Air- efficiency f\ 2 per cent

* One cheval vapeur is -985 of a horse power.

' Zeitschrif t des Vereines Deutscher Ingenieure, vol. xxxvi., page 1,446.

EXPERIMENTS WITH COMPRESSORS. 33

Tests of a Riedler Compressor at the Central Power Station,
Rue St. Fargeau, Paris, f— The results of four experiments
with this compressor are given in the following table. The
valves were mechanically controlled ; the diameters of the
cylinders were 1,090 mm. and 670 mm. (43 in. and 2 6 '4 in.)
with a stroke of 1,200 mm. (47 '2 in.) :—

Revolutions per minute ...................... 52 60 38 39

Horse power of air cylinders in chevaux vapeur. 615 709 422 424

Compression pressure in atmospheres absolute. . 7-0 7'0 7-0 7-0

Volumetric efficiency, per cent ................ 98'5 98'0 9S'5 98'5

Volume of free air per revolution, in cubic feet. 77'5 77*0 77 '5 77-5

Volume of free air in cubic feet per steam |
horse power per hour .................... f

Total efficiency ^ per cent .................... 747 747 79-4 81

Air efficiency tjz per cent ...................... 82'5 82'2 88'2 90

Mechanical efficiency, per cent ................ 90'6 91'0 90'1 90

We have added the last three lines. The total efficiency

144 x 14'7 x hyp. log 7
" - x 33000 x 60 *a

where va = volume of free air per steam horse power per
hour.

144 x 14-7 x hyp, log 7 V2.R
•985 x 33000 H

where V2 = volume of free air per revolution, R = revolu-
tions per minute, H = horse power of air cylinders, and the
mechanical efficiency is ^ -^ rj2.

Test of a Two-stage Compressor constructed by the Chicago
Pneumatic Tool Company. — The following are the results of
a test of a two-stage compressor having steam cylinders 16 in.
and 27 in. diameter, air cylinders 24 in. and 14 in., with 18 in.
stroke.

t Neue Erfahrungen ilber die Kraftversorgung von Paris durch Druckluft, von
Prof. A. Riedler.
4AC

AIR COMPRESSORS AND BLOWING ENGINES.

RESULTS OF TESTS of 24 C.S.C. compressor (running con-
densing). Duration of run 2J hours. Readings taken
every 15 minutes. Date, Jan. 1th, 1903.

Air cylinder data.

Average R.P.M 56-3.

Average receiver pressure 7S'l

Average temp. L.P. intake 58 -3

Average temp. L.P. discharge .. 216*0

Average temp. H.P. intake 82 '4

Degrees of heat extracted by

intercooler 136'6

Average temp, of discharge (H.P.) 182 "2
Temp, of air compressed to 78,

with no cooling 427'0

Total degrees of heat extracted by

jackets and intercooler 244'8

Average M.E. P., H.P. air (Hd.E) 87'0

Averagel.H.P., H.P. air (Hd.E) 14'6
Average M.E.P., H.P. air

(crank E) 37'9

Average I.H.P., il.P. air

(crank E) 14'9

Average I.H.P., H.P. air cylinder 29'5

Average M.E. P., L.P. air (Hd.E) 18-5

Averagel.H.P., L.P. air (Hd.E) 21'5
Average M.E. P., L.P. air

(crank E) 18'2

Average I.H.P., L.P. air

(crauk F) 21 2

Average I. H. P. , H. P. air cylinder 42 7

Total I. H.P. of H.P. and L.P.
air cylinders (29 -5— 42-7) 72 -2

Steam cylinder data.

Average R.P.M f>6'3

Average M.E. P., H.P. cyl. (Hd.E) 8:-4
Averagel.H.P., H.P. cyl. (Hd.E) 19 25
Average M.E. P., H.P. cylinder

(crank E) 42'8

Average I.H.P., H.P. cylinder

(crank E) 22-0

Total I.H.P., H.P. cylinder 41'25

Average M.E.P., L.P. cyl. (Hd.E) 12-6
Average I.H.P., L.P. cyl. (Hd.E) 19'4
Average M.E.P., L.P. cyl. (-rank) 14'55
Average I.H.P., L.P. cyl. (Hd.E) 21'16
Total I.H.P., L P. cylinder 40-56

Total I.H.P., Il.P., and L.P.
steam cylinder 81-81

Quality of steam 97 per cent dry
vacuum 26 '7 in.

Total weight of condensed ateam
for 2£ hours 4100

Actual steam for I. H.P. per hom-

4100

= 20-09

81'8 X 2-5

Dry steam per I. H.P. per hour
20-09 X 97 per cent = 19-487

Mechanical efficiency of com-

72 '2
pressor J — - = 88 '2 per cent.

Average intercooler gauge pressure 26'7

The above table shows that the volume swept out by the
L.P. piston was 533 cubic feet per minute ; to compress thia
to 78 '1 Ib per square inch by gauge or 92*8 absolute would
require '88 horse power.

EXPERIMENTS WITH COMPRESSORS.

92'8

147 x IU x 533 x 2-3 lo<

U =

U-7

33000

= 63-2.
The efficiency of compression

62*2

% = :7-rj^ = 87-2 percent,

AIR CYLINDER.

Diameter of cylinder, 11 in. ; stroVe, 14 in. ; R.P.M., 140 ; M.E.P., 41 '6 ; boiler
pressure, 95 ; air pressure, 100 ; I.H.P., 39 '1.

STEAM CYLINDER.

Diameter of cylinder, 12 in; stroke, 14 in; R.M.P., 140 ; M.E.P., 507; boiler
pressure 95 ; air pressure, 100 ; I.H.P , 56 '7.

FIG. 9.

and the total efficiency

Assuming a volumetric efficiency of 95*25 per cent, as in
the next example, these figures reduce to S3 and 72 '2 per
cent.

AIR COMPRESSORS AND BLOWING ENGINES.

Figs. 9 and 10 show the stearn and air diagrams of
another two-stage air compressor by the same firm. Measure-
ment of the diagrams shows that the volumetric efficiency

AIR CYLINDER.

Diameter of cylinder, 19in. : stroke, 14in. ; R.P.M., 140 ; M.E.P., IS'S ; boiler
pressure, 95 ; air pressure, 100 ; I.H.P., 52'9.

STEAM CYLINDER.

Diameter of cylinder, 12in. ; stroke, Hin. ; R.M.P., 140 ; M.E.P., 49 7 ; boiler
pressure, 95 ; air pressure, 100 ; I.H.P., 55 '6.

FIG. 10

is 95*25 per cent. The ideal mean effective pressure referred
to the low-pressure air piston is

0-9525 x 14-7hyp.log1 4'7

14-7

- 28-8.
The actual mean pressure is 3 2 -75.

28-8

Hence

32-75

= 88 per cent.

TEST OF A BREITFELD, DANEK COMPRESSOR. 37

The mechanical efficiency is

* = = 82 per

The total efficiency is therefore 72 '1 per cent.

The values of the exponents n for low-pressure and high-
pressure diagrams are 1*29 and 1'33.

One Steam H P cafhhresses 341

FIG. 11.

Test o/ a Two-stage Compressor Constructed by Messrs.
Breitfeld, Danek, and Co., of Prague, Karolinenthal. — The
combined diagram of the compression cylinders is shown in
fig. 11, for which I am indebted to the above firm. The
diameters of the steam cylinders are 675 mm. and 950 mm.
(26*6 in. and 37*45 in.), the blowing cylinders are 530 mm.
and 875 mm. (:JO'9 in. and 34'5 in.), and the stroke is
900 mm. (35 '5 in.) The engine is condensing, the admission
pressure 88 Ib. by gauge, and the air is compressed to 7

AIR COMPRESSORS AND BLOWING ENGINES.

atmospheres absolute. The speed was 68 revolutions per
minute, and the mechanical efficiency 88 per cent. The
mean effective pressures of the high and low pressure com-
pressing cylinders were 2 '85 and 1'25 atmospheres, and the
mean effective pressure referred to the low-pressure piston
was 2*39 atmospheres. The volumetric efficiency was 97
per cent, so that the mean effective pressure referred to the
low-pressure piston with isothermal compression would have
been

p = '97 x hyp. log 7 = 1'885 atmospheres.

The efficiency of compression and the total efficiency are

1>885
2*39

= 79 percent; >;x = 79 x -88 - 69*5 percent.

FIG. 12.

These experiments were made on the 20th and 21st of
June, 1903. On the former the temperature of the entering
air was between 27 deg. Gen. and 29 cleg. Cen. ; that of the air
entering the intermediate cooler between 115 deg. and 136
deg., which fell to between 50 cleg, and 57 deg. on leaving it.

VALVES FOR PRODUCING EQUALISATION OF PRESSURE. 39

The discharge temperature was from 124 deg. to 146 deg.,
and the rise of temperature of the cooling water was from
6J deg. to 10 deg.

CHAPTER III.
VALVES FOR PRODUCING EQUALISATION OF PRESSURE.

13. Theory of Valves for Producing Equalisation of
Pressure at the End of the Stroke. — In fig. 12 is shown a form
of valve for this purpose. The passages s, s in the cylinder,
corresponding to steam passages, are for the admission and
discharge of air from either side of the piston. The space a
is that through which air is admitted, and the space above
and around the valve is connected with the discharge pipe.
A valve bt similar to the distribution valve of a Meyer
expansion valve, has vertical passages at either end, which
are closed at the top by a plate c held down by the pressure
of the air above it, and by two spiral springs. There is also
a passage which we shall call the equalisation passage, which
connects the two passages s, s, and therefore both ends of the
cylinder. The inside edges of this passage coincide with
the inside edges of the passages *, s. By outside lap is
meant the distance between the outside edge of a passage s
and the inside edge of a vertical passage in b. The inside
lap is the distance between the inside edge of a passage s
and the corresponding iuside edge of the valve. Fig. 13
shows the crank c s and the eccentric s e, and the angle of
advance is h s <?, but the motion is in the opposite direction
to that of a steam engine, as shown by the arrow. Fig. 14
is the valve diagram, which is similar to a steam-engine
valve diagram. If c n and c r are the inside and outside
laps, while c p and c q are the widths of the equilibrium
passage, then when the valve is moving to the left, and is to
the left of mid-stroke by the amount c n, the eccentric centre
line, or briefly the eccentric, is at an angle q c d from the
dead centre, and the passage is just about to open. As the
valve moves further to the left the eccentric approaches

AIK COMPRESSORS AND BLOWING ENGINES.

the dead centre, and when the valve has moved c d from
mid-stroke the eccentric is on the dead centre. The valve
now commences to move back, and the left-hand passage s is
gradually closed. Inflow stops when the valve is a distance

FIG. 13.

c n to the left of mid-stroke and is moving to the right, and
the eccentric is then at c b — i.e., an angle bed from the dead
centre. As the eccentric rod is very long, the motion is
practically harmonic, and g n b is perpendicular to d s.
When the valve is a distance c p to the left of mid-stroke,
and the right-hand end of the equalisation passage just about

FIG. 14.

to open to the right-hand passage s, equalisation of pressure
commences, the air flowing from the right to the left side of
the piston, the eccentric being now k c d from the dead
centre.

VALVES FOR PRODUCING EQUALISATION OF PRESSURE. 41

The valve passes over its middle position, that shown in
fig. 12, and when it is a distance c q to the right of mid-
stroke equilibrium ceases, and the air on the left of the
piston is compressed by its motion to the left. When the
valve is c r to the right of mid-stroke, the vertical passage
in b on the left opens to the passage s, and air would be
expelled were it not for the valve c, which does not rise
until the pressure beneath becomes a trifle greater than that
above. The valve moves to the end of its stroke to the
right, and returns, closing the left passage s, so that discharge
ceases; and we shall show that if cr = en, this will be at
the end of the stroke of the piston to the left. When the
valve is cq from mid-stroke and moving to the left, the
left-hand end of the equalisation passage is just about to
open, and the right-hand end closes when the valve is cp to
the left of mid-stroke. While, therefore, the eccentric
moves through the angle I c h equilibrium takes place.
Admission on the left again takes place when the valve is c n
to the left of mid-stroke. Thus d s may be looked on as the
line of stroke of the valve g c, cb, ck, etc., as the positions
of the eccentric relative to it when the valve is en, cp, etc.,
from its mid-stroke, and d s may be called the valve line.
The crank leads the eccentric by the angle c s e, fig. 13; so
that if a line a c b be drawn making the angle a c d equal to
c s e, fig. 13, then, if a eg be the angle the crank makes with
the line of stroke, and g n c is a right angle, then the valve
is c n to the left of mid-stroke, and similarly for the other
positions. So that eg is the position of the crank when
admission commences and c b when it ceases ; c k and c I are
the positions when equalisation of pressure commences, c m
and c h when it ceases ; c t and c a when the left vertical
passage in the valve is connected to and cut off from 5. In
the triangles arc, cnb the angles at c are equal, and. those
at n and r are right angles, a c being equal to c. b. Therefore
c r and c n are equal, and the outside lap of the valve is
equal to the inside, and these and the angle of advance are
evidentlv determined by eg ; c 6-niust be on the stroke line,
and ccfmust bisect the angle g c b. In fig. 15 the con-
nection between the indicator diagram and c g is shown.
Between b and 7j, a and I, fig. 14, there will be a slight

AIR COMPRESSORS AND BLOWING ENGINES.

compression of the air from the atmospheric line on the left
and right of the piston respectively, but the portion of the
stroke travelled is so small that these may be neglected.

In fig. 15, instead of ft. being vertical and the commence-
ment of the expansion curve e d being at e, there should at
first be expansion, as shown dotted by fl, while the crank
travels from a to £, fig, 14, then equalisation, causing the
drop / m (supposed instantaneous) ; following this m h, a very

FIG. 15.

short horizontal line, exaggerated in fig. 15, while the crank
travels from I to h, fig. 14; and finally expansion h k, while
the crank moves from h to g. Similarly, there will be com-
pression n p, equalisation p g, a horizontal line q r, and
compression r s, fig. 1 5, while the crank passes over 6 &, km,
and part of the arc t a. The points r and h are, however,
so very close to the ends of the indicator diagram that
equalisation may be supposed to take place at the end of
the stroke, and instantaneously, and d calculated on this
assumption. This fixes g, which is directly above d if we
neglect the effect due to the obliquity of the connecting rod,

VALVES FOR PRODUCING EQUALISATION OF PRESSURE. 43

and if g c b is bisected by u c t, the angle of advance is vet.
Joining b <?, we have the mean inside lap c w, which also
equals the mean outside lap. In order to find the actual
values for both ends of the valve, allowing for the obliquity
of the connecting rod, we must proceed as in fig. 16.
Suppose the crank to the left of the figure ; draw a b, ut as
in fig. 15, and mark off m and p, the points of admission, so
that m b and a p are equal to d n in fig. 15. Draw m g and
pgz perpendiculars to a b. Then, as before, en and c r give
the laps, neglecting obliquity of the connecting rod ; from

FIG. 16.

centres on b a produced draw two arc of circles m gl and p g*.
Then at the commencement of admission the crank will be
atc<7i and c gs. Drop perpendiculars g-i^b^ and gsriat
upon u t ; then the inside lap on the left must be c n-L and
that on the right c r^ so that admission will cease at ^ and
as, but as these points are so near the dead centre, this will
be of no consequence. The outside laps should have the
mean value c n, so that discharge will cease exactly at a and
b. The position of the point d, fig. 15, depends, of course,
upon the exponent chosen for the expansion curve ;

1-25

is a good value.

44 AIR COMPRESSORS AND BLOWING ENGINES.

CHAPTER IV.
BLOWING P^NGINES.

14. These are used for supplying air to blast furnaces and
Bessemer converters. In the former pressures of half an
atmosphere by gauge used to be customary, but now, following
American practice, we find this is being increased to 20 Ib.
above the atmosphere. Bessemer blowing engines supply
air at a pressure of 1^ to 2 atmospheres by gauge, or 22.^ Ib.
to 30 Ib.

Blowing engines are of very large size and power in
consequence of the large amounts of air required. Many
beam engines are still in use, but modern practice prefers
the horizontal or vertical direct-acting type, in which each
of two steam pistons drives an air piston by means of its
tail rod. The steam cylinders are therefore in the middle of
the engine, and on the other side of them from that on which
are the blowing cylinders is the crank shaft, which usually
has two overhung cranks, generally set at right angles, with
a flywheel between them. In vertical engines the blowing
cylinders are at the top. The air valves are self-acting or
mechanically controlled, and the steam valves are of many
different types, slide, Corliss, and conical valves being used.
In old-fashioned blowing engines we find low piston speeds,
such as 240 ft. per minute, with 8 ft. stroke, and therefore
15 revolutions; but improvements, especially in the air
valves, have made speeds of 450 ft. per minute possible, even
with self-acting valves. We shall first describe a number of
blast-furnace blowing engines, and afterwards deal with the
Bessemer type.

15. Blast-furnace Blowing Engine, constructed by L.
Lang, Budapest, for the Kdniolich ungarisc/ten Eisen und
Stahlwerks, Vajdafiungad.* — Figs. 17 and 18 show the
general arrangement in plan and elevation. There are two
blowing cylinders of 2,070mm. (81 '6 in.) diameter, whose
pistons are driven direct from those of the two steam

* Stahl und Eisen, 1897, No. 22.

BLOWING ENGINES.

AIR COMPRESSORS AND BLOWING ENGINES.

BLOWING ENGINES.

cylinders, whose diameters are 725 and 1,150 mm. (28'5 and
45 '2 in.), the stroke being 1,350 mm. (53 '1 in.) ; the number
of revolutions per minute is 40 to 50, and the steam pressure

120 Ib. The air is discharged at a pressure of 18 to 25 cms.
of mercury, or 7'1 to 9 -85 Ib. per square inch, and the
volume discharged lies between 700 and 900 cubic metres,

AIR COMPRESSORS AND BLOWING ENGINES.

or 24,600 to 31,700 cubic feet per minute. The air pump
is horizontal and double acting, lies beneath the floor, and
is driven by a lever whose upper end is attached to the
guide block of the blowing cylinder piston rod on the high-
pressure engine side. The air is drawn in through two

passages in the foundation which are connected with a
chimney. The discharge pipe is seen in fig. 17. The
valves are double beat, and are driven by Collmann's valve
gear, fig. 19. The high-pressure cut-off is varied by the
governor, and the low-pressure by hand.

BLOWING ENGINES. 49

Fig. 20 shows a transverse section and end view ojfthe
blowing cylinders, while figs. 21 and 22 show the ralve
chest, and figs. 23 and 24 the valve construction, whiih is
the most interesting part of this engine. Fig. 23, on, the
left, shows to a reduced scale views of the suction ' and
discharge valves, and on the right two half sections, the
upper one that of the suction valve, and the lower that of
the discharge valve. Fig. 24 contains a view perpendicular
to the axis of the valve, while above and below are sections
of the valve guards or stops. In fig. 23 will be seen the
thin plate of steel which forms the suction valve. It is
O'Smm. ('0315 in.) thick, and has an external diameter of
244 mm. (9 '6 in.), and an internal diameter of 120 mm.
(4 7 2 in.). On its left is the valve-seat casting of steel,
having two concentric rings of V section forming valve seats,
The sectioning and vertical line to the right of the figure
represents the piston at the end of its stroke, and gives
some idea of the clearance space. To the left of this is the
valve guard of cast steel, held to the valve seat by the
central bolt ; and finally, there are three strips of steel plate
F K, fig. 24, which are riveted at their ends F to the valve
guard, and at K to the valve, so that it moves to and fro
without friction, and, as the moving mass is very small,
without shock, nor can it get jammed in any way. When
fully open the valve ring rests upon two narrow concentric
broken rings on the guard, which are shown shaded in the
central drawing of fig. 24, and which are not continuous, in
order to leave space for the end of the plate springs F K.
The upper half of this drawing shows the suction valve
guard, as seen from the left, with the three springs, the
valve being supposed removed, its position indicated by the
two dotted circles. The lower half of this figure shows
the delivery valve guard, the springs being shown dotted
and the valve sectioned. The valve guards are shown in
section in the upper and lower views, the former having
valve and springs in place.

The discharge valve differs from the suction only in being
formed of two plates, the outer one 0'4 mm. thick ('015 in.),
a space of half a millimetre being left between the two. The
suction valve has to open when the crank is near the dead

5AC

50 AIR COMPRESSORS AND BLOWING ENGINES.

BLOWING ENGINES.

52 AIR COMPRESSORS AND BLOWING ENGINES.

centre, but the delivery valves, when it is in rapid motion ;
so that an oil or air cushion is provided by the space between
the plates to lessen the shock. The arrows in fig. 23 show
the direction in which the air flows through the valve. Fig.
22, on the extreme right, shows a front elevation of the
valve seat cover, which, according to the custom adopted
for leather clack valves, is divided into two unequal parts,
one third of the area — the upper part — being for the delivery
valves, and the remainder for the suction. When the engine
was constructed these valves were a novelty, and the
purchaser required that the valve seat cover should be so
constructed that in the event of the valves working unsatis-
factorily they might be replaced by ordinary leather clack
valves. In order to provide for this the cover had to be
made in the complicated grating form shown in the figure,
and a false cylinder flange had to be bolted to the cylinder
flange, as the valve seat cover took up more room than it would
have done had provision only to be made for the new valves.
In later designs fewer and larger valves are fitted, the
number of the suction being equal to that of the delivery
valves, the former having a greater stroke. The best
number is nine of each, having a diameter one-sixth that of
the cylinder, and the whole of the valve can be cast in one
piece, as in the Bessemer blowing engine for the Reschitza
Ironworks, in South Hungary, and the blast-furnace blowing-
engine for the Aplerbecker works. For long-stroke engines
with high piston speed, and for vertical engines, the valves
can be placed in a ring at the cylinder end, although
this slightly increases the clearance, which still, however,
remains much below that usually found with self-acting or
mechanically-controlled valves.

It will be noticed that in fig. 21 the valve seat is pressed
into the inner cover by means of the central bolt. The
valve is packed by means of three or four turns of cord
soaked in boiled varnish. Each hand-hole cover has a glass
window through which the working of the valves can be
observed. At the top of the same figure will be seen a
valve which can be closed when a discharge valve has to be
withdrawn. To do this it is first necessary to withdraw
three or four suction valves from the same end of the

BLOWING ENGINES.

cylinder, so that the air drawn in at each stroke can be
again discharged through them. The valve above mentioned
may then be closed, and one cf the hand holes in the upper

re-

of the cover opened, the valve withdrawn, and a new
one put in its place. The valve chest need only be removed
\rhen the piston requires repair. As a matter of fact, during
the first two arid a half years, during which the engine was

54 AIR COMPRESSORS AND BLOWING ENGINES.

continually at work, no repairs were required. The actual
sizes of valves constructed are 260, 280, 300, 320, and
340mm. diameter (10'25, 11 -8, 12'6, and 13'4in.), with
strokes of 15 to 30 mm. ('59 to 1'18 in.). It is only where
the pressure is low that a V section can be given to the
valve seat, and for compressors the form shown in fig. 25 is
used. In order to avoid the necessity of using a thicker
plate for the valve there is a third intermediate seat. Fig.
26 is a plan. The upper half of each figure shows the
delivery valve, and the lower the suction valve, in each case
with the guard removed.

15. Blast-furnace Blowing Engine, constructed ly Breit-
feld, Danek, and Co., of Prag-Karolinenthal. — The leading
dimensions of this engine are : —

Diameter of high-pressure cylinder 900mm. (35*4 in.)

Diameter of low-pressure cylinder 1,380 mm. (54'4 in.)

Diameter of both blowing cylinders 1,950 mm. (76'8 in.)

Stroke 1,400mm. (55-1 in.)

The steam cylinders have Corliss valves, the high-pressure
under the control of the governor, the low-pressure cut-off
being adjustable by hand. As the speed can be varied
between 33 and 53 revolutions per roinute, the Proell
governor has its lever fitted with two weights, the adjust-
ment of which modifies the speed. The engine is jet-con-
densing, a double-acting horizontal air pump being placed
beneath the floor and driven by means of a coupling rod and
bell crank from the low-pressure crank pin. Its diameter is
640 mm. (25'2 in.), and its stroke about 546 mm. (21 '5 in.).
The discharge is 650 cubic metres (22,850 cubic feet), at
43 revolutions per minute ; 760 cubic metres (26,700 cubic
feet), at 50 revolutions ; and 800 cubic metres (28,100 cubic
feet), at 52J revolutions. The highest air pressure is
0*7 kg. per square centimetre (nearly 10 Ib. per square inch),
and the pressure of the steam at the engine llOlb. per
square inch, and about 18 expansions.

Fig. 27 shows a side elevation and fig. 28 a plan of the
blowing cylinders; the left-hand half of the former is an
outside elevation. The valve gear, being on the further side
of the cylinder, is shown dotted. It consists of a wrist plate

BLOWING ENGINES.

having three arms, the middle one being driven by an
eccentric, and each of the other two driving a discharge and
suction valve. The gear is so arranged that the valves open
rapidly, but their motion while they are closed is extremely
small, thus reducing wear and work wasted in friction ; the
valves, of course, are of the Corliss type. The lower valves
control the admission of the air, but as the moment of

FIG. 27.

discharge depends on the pressure in the discharge pipes,
self-acting valves are fitted above the Corliss discharge
valves, there being 20 at each end of the cylinder. The
cylinder ends and covers are shown in figs. 29, 30, and

31, and a larger view of one of the self-acting valves in fig.

32. The Corliss discharge valves close just at the end of
the stroke, so that the space above them is filled with air at
discharge pressure. The self-acting valves consequently
return to their seats quietly, and this all the more so

AIR COMPRESSORS AND BLOWING ENGINES.

~rf% ~

fl f^ ft

"r ?5"-"¥

.o->

- -

=£

.0'

0
.0

.<J

Ji' ' 1 ' IB

=S£

;

.0]

•-<

0
r^

_ L

*
'?>

.'"S

FIG. 28.

BLOWING ENGINES.

because, their guides being screwed spirally, their descent is
somewhat checked. Owing to the fact that the Corliss

FIG. 29.

FIG. 30.

valves cut off the cylinder from the pressure pipes, the
self-acting valves need not close rapidly, and have the time
of a little more than one stroke to do so.

AIR COMPRESSORS AND BLOWING ENGINES.

The Corliss valves are shown in plan in fig. 28. The
section of the suction Corliss valve opening is 2,100 sq. cms.
(326 sq. in.), that of the discharge valve is 1,800 sq. cms.
(279 sq. in.), that of 20 self-acting valves 2,450 sq. cms.

FIG. 31.

FIG. 32.

(380 sq. in.), and that of the blowing cylinder 29,515 sq. cms,
(4,570 sq. in.). The corresponding ratios are — 1 : 14.
1 : 16 '4, and 1 : 12. The corresponding velocities at 33
revolutions are 21 '6m. per second (70'75 ft. per second),

FIG. 33.

25 '3 m. per second (83ft. per second), and 18 -5 m. per
second (60-6ft. per second); at 53 revolutions, the highest
speed, these become 34'6, 40'5, and 29*6 m. per second
(113, 132-5, and 97ft. per second). The corresponding
piston speeds are 303 ft. and 486 ft. per minute. The air is
drawn into the cylinders from a passage beneath. The

BLOWING ENGINES.

5t>

FIG. 34.

AIR COMPRESSORS AND BLOWING ENGINES.

connections with the discharge pipe are not shown in the
figures. Figs. 29 and 30 show that the discharge valves
are easily accessible through a number of hand holes above
them. Fig. 33 is a section through the blowing piston,
which is of cast steel.

The engines were tested by Prof. E. Hermann, on August
20th, 1897, before the engines were connected to the blast

-0,5

FIG. 35.

furnaces, the pressure of the discharge being raised by
throttle valves in the discharge passages. The experiments
gave the following results : —

Horse power of H.P. cylinder (chevaux vapeur) .... 304*91.

Horse power of L.P. cylinder (chevaux vapeur) 333*01.

Total horse power (chevaux vapeur) 637*92.

Blowing cylinder, horse power (chevaux vapeur) ... 547*08.

Mechanical efficiency, per cent 85*75.

Steam per horse power hour 15*21b.

BLOWING ENGINES. 61

Fig. 34 shows the combined diagrams of the steam
cylinders, and fig. 35 the blowing diagrams. Of these
latter the upper were taken during the experiments, and the
lower when the engines were at work. The irregularity of
the suction lines is due to the closing during the experi-
ments of one of the suction passages, and the rise of the
discharge pressure at the middle of the stroke to the throttle
valves. The manometer showed 0'37 of an atmosphere
during the experiments, but with such peculiar diagrams it
would evidently be unfair to calculate from them the
efficiency of compression or the total efficiency of the engines.
The lower diagrams have a mean effective pressure of
8 '05 Ib. per square inch, so that the efficiency of compression

•976 x 14-7 hyp. log 1-64

7/2 = ~ 8-05 = 88 Per cent,

the volumetric efficiency being 97*6 per cent, and the
discharge pressure 1*64 atmosphere absolute. This, with
the mechanical efficiency obtained during the experiment,
would give a total efficiency

??! = 88 x -8575 = 75-6 per cent.

I5a. Blast Furnace Blowing Engine constructed ly the
Sdchsischen Maschinenfabrik^Chtmnitz. — The leading dimen-
sions of this engine are : —

Diameter of each steam cylinder... 1,100 mm.-(43'4 in.)
Diameter of each blowing cylinder 2,350 mm. (92*6 in.)
Stroke 1,800mm. (71'9in.)

The independent condensing engine, placed beneath the
floor, has the following leading dimensions : —

Diameter of steam cylinder 450mm. (17'75 in.)

Air pump cylinder diameter 550 mm. (21 '65 in.)

Stroke 680 mm. (26'8 in.)

The boiler pressure is 60 Ib., with a cut-off at 12 per cent
of the stroke ; the discharge, at 30 revolutions per minute,
is 900 cubic metres or 31,700 cubic feet of air per minute of
free air, which is delivered at a pressure of -^ths of an
atmosphere, or 5'88lb. per square inch. The speed can be

<52 AIR COMPRESSORS AND BLOWING ENGINES.

Fio. 36.

BLOWING ENGINE?. 63

varied between 16 and 38 revolutions per minute by a
change in the load of the governor. The mechanical
efficiency was found to be 86 per cent, and the pressure 0*46
of an atmosphere at 35 revolutions per minute, at which
speed the engine ran very quietly.

FIG. 38.

Figs. 36, 37, 38, 39, and 40, for which we are indebted to
the makers, are a sectional elevation of the blowing cylinder ;
a sectional plan of the same ; a transverse section through
the valve chest, showing the delivery valves, the suction

AIR COMPRESSORS AND BLOWING ENGINES.

passages, and the throttle valve, by means of which the
cylinder may be cut off from the pressure pipes ; an end
view, looking from the steam cylinders; and an elevation,
partly in section, of the whole engine.

As shown in fig. 38, one-third of the area of the cylinder
end contains the delivery valves, and two-thirds the suction.
They are all of leather, each is fastened in the middle by
three screws, and each covers 6 or 10 passages; there are 24
suction valves at each end and 12 delivery. The two upper

sections are, of course, separated by ribs from the four lower,
and the area of the discharge valves is one-eighth that of the
cylinder, while that of the suction is one-fifth.

Fig. 36 shows that the engine is supported by two funnel-
shaped castings, through which the air flows from a passage
in the foundation, so that the air may reach the engine as

BLOWING ENGINES.

6AC

66 AIR COMPRESSORS AND BLOWING ENGINES.

BLOWING ENGINES.

cool as .possible. We may note here that this does not
influence the work per stroke, which depends on the volume
of air drawn in, but it directly affects the weight of air
delivered, which is, of course, of importance in a blowing
engine. The speed of the engine is controlled by varying
the expansion, the valves, of which there are four, being
driven by eccentrics on a pair of side shafts.

16. Blast-furnace Blowing Engine by Messrs. Schneider
and Company, Creus6t.*—l?iga. 41 and 42 show a horizontal

FIG. 43.

FIG. 44.

blowing engine with one steam cylinder 750 mm. (29 '53 in.)
diameter, and one blowing cylinder 1,770mm. (69'69 in.)
diameter, with a stroke of 1,400mm. (55*12 in.). The
steam cylinder has Corliss valves, arid the blowing cylinder
small metal valves, the discs of which are fitted with light
closing springs. These discs are of special steel made at
Creusot, have considerable durability, and can be easily
replaced. The inlet valves are arranged on the lower half

From Engineering, February 4th, 189S.

68 AIR COMPRESSORS AND BLOWING ENGINES.

of the air cylinder, and the outlet on the upper half, figs. 43
and 44. The former figure shows a section, and the latter
an end view of the cylinder. There are 150 inlet valves at
each end, giving an area of 2*969 square feet, and 180 outlet
valves, whose area is 3*56 square feet. As the effective
section of the cylinder is 26 -39 square feet, these are
0-1125 and 0*135 of the cylinder area. The weight of the
flywheel is 11 tons, the indicated horse power 378, and that
of the air cylinders 288, giving a mechanical efficiency of

" Scale )0fa. 3 k-1
JS/Tective area. oC tybndtr 0^m4HOQ

Jlevs per Tnuv BO
FIG. 45. — Diagrams from Steam Cylinders.

7 6 -25 per cent. The blowing cylinder is connected to a
reservoir, common to six machines, from which the service
mains are taken that distribute the cold air to Cowper
heating stoves. Each engine can be isolated from the
reservoirs by means of valves placed upon the upper side
of the pressure chamber. Indicator diagrams are given in
figs. 45 and 46. The ratio of the mean atmospheric
pressure and the absolute pressure to which the air is
compressed is

29-92 + 11-81 41-73

r =

29-92

The volumetric efficiency is 98 per cent, disregarding the
fact that the suction pressure is less than that of the
atmosphere. The ideal horse power with 50 revolutions per
minute is

14-7 x 144 x 26-39 x 55-12 x 100 x 2-3 x -146
12 x 33000

261.

BLOWING ENGINES.

The air efficiency is therefore
261

= 90 '6 per cent,

but the total efficiency is

261

^i = J^ -- 69 per cent.
o t o

Fig. 47 shows the governor,* which controls both speed
and pressure. A is the speed governor, which acts on a
sleeve in the usual way, and lowers or raises the lever

Socde 6%u'

Area, of Cylinder 2**

Front' liecav preoearf 0*d8Q

.. Stroke WO....

ticuok

&as_

rtatarc-c*.

Air Pntawt 30 %> of Mercury • 0*408
Fio. 46. — Diagrams from Air Cylinder.

beneath it, whose fulcrum is slightly to the left of its axis.
A vertical arm, which has attached to its upper end a
connecting link, acts by means of this upon the trip cam of
the Corliss valve motion. But the horizontal lever is also
acted on by the air piston B, the weight E, and the adjust-
ment spring F. Air pressure acts on the under side of B,
so that when the pressure is in excess of a certain desired
quantity the lever is raised, and the cut-off in the steam
cylinder takes place sooner. C is an oil brake to destroy
oscillations, and D is the governor weight. The maximum
engine speed is 54 revolutions, and the variation of pressure
does not amount to '39 in. of mercury above or below the
normal.

ion d'Air, from the Bulletin de la Societe de 1'Industrie

AIR COMPRESSORS AND BLOWING ENGINES.

17. Delivery Valves constructed by the Gutehoffnungshiitte,
Oberhausen a. d. Ruhr. — Fig. 48 is one of the delivery

valves for a 500 horse power blast-furnace blowing engine.
A portion of the piston is shown at the end of the stroke,
and the valve is closed. An indiarubber cushion, fixed to

BLOWING ENGINES.

.71

72 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. 49

BLOWING ENGINES.

the piston, is pressing the valve against the valve-box cover,
which is held down by a spiral spring, and the valve itself is
closing the delivery passages by its larger piston, whose
diameter is 265 mm., or 10 -±5 in. When the piston returns
the valve remains in the position shown, because the
pressure on the inside is less than that on the outside, which
comes on the under side of the piston through the small
holes in the valve box. When, however, the piston returns

FIG. 50.

and the pressure again rises, the difference of the pressures
on the inside and outside of the valve acting on the ring
area, whose outer diameter is 265mm., and inner 180, or
7'1 in., forces it open again until it is closed by the piston
at the end of the stroke. The stroke of this valve is 26 mm.,
or 1'02 in. Bessemer blowing engines are fitted with similar
valves.

AIR COMPRESSORS AND BLOWING ENGINES.

18. Blast-furnace Blowing Engine Cylinder, constructed
by the Guteho/nungshutte.—Figs. 49, 50, and 51 show the
cover of a blowing cylinder, whose diameter is 1,300 mm.

FIG. 51.

(51 -2 in.), and stroke 750mm. (29 '5 in.) Fig. 49 is a side
elevation, fig. 50 an end elevation looking from the inside,
and on the right a sectional elevation through the axis, bufc

BLOWING ENGINES.

AIR COMPRESSORS AND BLOWING ENGINES.

passing through the centre of one of the upper valve seats.
Fig. 51, on the left-hand side of the upper view, is a sectional
elevation by a plane perpendicular to the axis of the cylinder
and passing through the axis of the Corliss suction-valve
chest. The right half of the upper view is an outside eleva

FIG. 53:

FIG. 54.

FJG. 55.

tion; the left half of the lower view is a sectional plan
through the axis of the suction-valve chest, and the right
half is taken through the centre of the lowest discharge
valve. The other cover differs in nothing of importance
from this.

A. discharge valve is shown in fig. 52, and has a diameter
of 160 mm. (6'3 in.). The action of this valve is the same

BLOWING ENGINES.

78 AIR COMPRESSORS AND BLOWING ENGINES.

as that shown in fig. 48, the piston closing it at the end of
the stroke. The general thickness of the cover is 35 mm.
(l'38in.),- of the top and bottom flanges 40mm. (1*58 in.),
and of the flange connecting it to the cylinder 45 mm.
(1*77 in.), while that of the end is 55 mm. (2'17 in.). Figs.
53, 54, and 55 show the cylinder, whose thickness is
35mm., and that of the flange 45 mm. The facing for the
wrist-plate bracket is shown in fig. 53.

19. Blast Furnace Blowing Engine constructed by the
Friedrich-Wilkelms Hitite, of Muklkeim a.d. Ruhr. — Fig. 56
shows a transverse section through part of the cylinder of a
large blowing engine, and fig. 57 a front elevation, partly in
section. The diameter is 2,200 mm. (86'6 in.) and the
stroke 59'1 in. The admission valves are of the Corliss
type, which are oscillated by means of levers, connecting
links, and a wrist plate driven by an eccentric, which is set
100 deg. behind the crank. The diameter of the valve
is 400 mm. (15| in.), and it is double ported, with an overlap
of about 1 J mm. ('06 in.). The lever that actuates the valve
is 350 mm., and it is set at about 63 deg. to the vertical
when the wrist plate is in its middle position. The valve
oscillates through an angle of 40J deg., but of this only
8 deg. are traversed while the valve is closed and there is
any pressure upon it. At admission the angular velocity of
the valve is seven-tenths of that of the wrist plate. The
length of the connecting link can be adjusted. The valve
diagram is shown below the wrist plate, the shaded part
referring to the period during which the valve is open. The
diameter of this circle that represents the piston stroke is
inclined at 10 deg. to the vertical, and projected from this
on the right is the indicator diagram. It will be seen that
the admission commences shortly after the commencement
of the stroke, when expansion from the clearance has ended,
and the passage is again closed very s^oon after the end of
the stroke. The compression is to seven-tenths of an
atmosphere. The wrist plate oscillates through an angle of
65 deg., the arms that drive the connecting links being
420 mm. (16iin.), and that actuated by the eccentric rod
300 mm. (11 '8 in.), the throw of the eccentric — i.e., its
eccentricity — being 160 mm. (6*3 in.). The discharge valves

BLOWING ENGINES. 7<J

are located in the upper half of the cylinder end ; they are
not shown in place in figs. 56 and 57.

. Fig. 58 is a sectional elevation through a valve, and fig.
59 another transverse to the axis, the right half showing the
cover, the left a section through the discharge ports in the
seat. The valve is of steel, its smaller diameter being
166 mm. (6-54in.), and its larger 245 mm. (9*65 in.). It is

Fio. 58.

closed in the drawing, having been pushed against the
plate of wrought iron, 8 mm. thick, by the piston at the
end of its stroke. This plate is prevented from moving to
the left by the ribs between the passages in the valve seat,
and it is pressed against them by the spiral spring, which
gives way when the valve is pushed against the plate. The
spring is of 11 mm. diameter, and the diameter of its coil
is 200 mm. The passages in the valve seat are 35 mm.
(1-38 in.) wide, and the valve moving to the left opens them

AIR COMPEESSORS AND BLOWING ENGINES.

fully. Once closed the valve is kept in that position,
because the pressure in the cylinder is less than that in the
valve chest directly the piston commences its return stroke.
The latter pressure enters the cylindrical valve seat by
means of the holes countersunk on the outside, and, acting
on the annular area of the valve, forces it to the right.

Fio. 59.

In order to cushion the valve when opening, these holes can
be closed, if necessary, by screws, so as to throttle the out-
flow of the air. As soon as the pressure in the cylinder
becomes slightly greater than that in the valve chest the
valve is forced to the left, and the passages opened. The
spring is kept in place by the casting, which also forms the
cover.

20. Blast-furnace Blowing Engine, constructed by Messrs.
Breiifeld, Danek, and (7o., of Prag-Karolinenthal. — Figs.
60, 61, and 62 show this engine in side elevation, front
elevation, and plan. It was constructed for the Wilkowitz
Ironworks, and is a compound-condensing engine, having
steam cylinders 1,500 and 2,000 mm. (59'1 and 78'7 in.)

BLOWING ENGINES.

7AC

AIR COMPRESSORS AND BLOWING ENGINES.

BLOWING ENGINES.

diameter, with blowing cylinders 2,400 mm. (94-5 in.)
diameter, and stroke 1,300mm. (51-25 in.). The speed is
45 to 65 revolutions, the boiler pressure 132 Ibs., and that

of compression I'l atmospheres by gauge. The discharge
per minute is 1,000 to 1,444 c.m. (35,200 to 50,900 cubic
feet) per minute, and the number of discharge valves in each
cylinder end 16. The arrangement of the engine is peculiar,

84 AIR COMPRESSORS AND BLOWING ENGINES.

but it combines the advantages of vertical and horizontal
engines. Each steam cylinder drives a blowing cylinder by
a lever beneath it, fig. 60, while the third arm of this lever
is coupled to the connecting rod, which drives a crank. The
shaft carries a flywheel in the middle, whose diameter is
6,030mm. (237 in.), the radial width of rim 400mm.
(15fin.), and breadth 235mm. (9'65in.). The distance
between the centres of the steam cylinders is 3,800mm.
(149'5 in.), and between each steam cylinder and the blowing
cylinder that it drives, 2,900 mm. (114 in.) The air pump is
to the right of the engine, and is driven by an overhung
crank and oscillating lever at the end of the crank shaft.
One of the discharge valves is shown in fig. 63. In a four
hours' test the mean speed was 44| revolutions very nearly,
the steam horse power 1576 '85, and that of the blowing
cylinders 1517'31, giving a mechanical efficiency of 96*22
per cent. The steam used per horse power hour was 15'llb.
Unfortunately the pressure of the air is not given, and we
cannot, therefore, find the total efficiency of the engine.

21. 500 Horse Power Double-acting Korting Gas JSngine
and Blowing Cylinder^ constructed by the Sieyener Maschinen-
lau Actitn-Gesellschaft. — The principal dimensions of this
engine are : —

Motor cylinder diameter, 635 mm. (26 '87 in.)
Stroke, 1,100 mm. (43'31 in.)
Blowing cylinder diameter, 1,750 mm. (69 in.)
Air pump diameter, 690 mm. (27*2 in.)
Gas pump diameter, 750 mm, (29*5 in.)
Stroke (about) 820 mm. (32'3in.)

Mechanically controlled Corliss valves are used for
admission of air to the blowing cylinder, the air entering as
usual by a passage in the foundations. The discharge valves
are of the Riedler-Stumpf type, which are closed by the
piston, but are opened by the pressure of air in the cylinder.
Fig. 64 is a sectional elevation, and fig. 65 a complete plan of
the blowing cylinder. Owing to the fact that the gases
from blast furnaces can now be employed to more advantage
in driving gas engines than in burning them in boilers, the
construction of the Korting gas engine, which is double

BLOWING ENGINES.

AIR COMPRESSORS AND BLOWING ENGINES.

acting, and therefore very compact, is of interest in connec-
tion with the subject of blowing engines. We therefore
give a description of this type of engine, for which we are
indebted to Messrs. Fraser and Chalmers, of Erith.

Fig. 66 is a plan showing a section through the motor
cylinder K, and the air and gas cylinders, L P and G P,

FIG. 64.

these being driven by a crank on the end of the engine
shaft. An eccentric between the crank and the bearing-
drives the slide valves of these cylinders, while the admission
valves E, figs. 67 and 68, are driven by cams on a side shaft
running at the same speed as the engine. There is no

BLOWING ENGINES.

exhaust valve, but passages S, figs. 66 and 67, are uncovered
at the end of the stroke, and the gases escape into a ring-
shaped passage leading to the exhaust pipe at A. Before
the exhaust passages are closed the admission valves open,
and as the pressure in the pump cylinders is about 9 Ib. per
square inch, the fresh charge enters the motor cylinder,

Fio. 65.

sweeping out the exhaust gases. Shortly after these
passages are closed by the returning piston, the pistons of
the gas and air pumps have reached their dead point. The
supply of fresh mixture therefore ceases, the inlet valves
close, and the charge in the cylinder is compressed, as shown
by a b in the diagram, fig. 67 ; at the dead centre explosion
b c occurs, followed by expansion c d, and exhaust d a on the
next stroke. A. layer of pure air is sent between the burnt
and the explosive charges, in order to prevent the new

AIR COMPRESSORS AND BLOWING ENGINES.

BLOWING ENGINES.

FIQ. 68.

90 AIR COMPRESSORS AND BLOWING ENGINES.

charge being mixed with the residues of the previous stroke,
so that dangerous pre-ignitions are avoided. The pumps do
not compress the charge, but only force it into the cylinder,
delivering to the admission valve through separate channels,
which are rather long, the gas and air being stored in these
channels.

It is evident that such of the two gases will enter the
cylinder first which fills the channels in the immediate
neighbourhood of the admission valve at the moment when
the valve is opened. Due to the setting of the slide valves
of the air pumps separately, and at different angles of
eccentric, the air pump takes in and discharges its fall
volume in the usual way, but in the gas pump the opening
and closing of the valves only takes place after part of its
stroke. During about the first half of its discharge stroke,
the gas taken into the pump cylinder is passed back to the
suction chamber which is in communication with it. Only
during the last half of the discharge stroke the work of the
gas pump actually begins, when connection between the
suction and pressure chambers is closed. The gas pump
then discharges at once to its full capacity for the remainder
ot its stroke. The air pump compresses the air contained
in the cylinder from the commencement of the discharge
stroke, and so air always enters the power cylinder ahead of
the mixture of air and gas, and will always be found between
the burnt and explosive charges.

It must be understood that the combustible mixture of
gas and air is only formed at the exact moment of its
entrance in the cylinder at E. The pure air entering first
into the power cylinder does not mix with the combustible
mixture on account of the special arrangement of the inlet
bend. The charge is not diluted, and even a small charge
can be ignited and burnt. The composition of the mixture
of gas and air remains constant, the governor regulating the
volume of the mixture, according to the power required for
each stroke. The regulation can be effected in two different
ways : —

1. The moment when the gas pump begins to discharge
may be retarded, i.e., the connection between the pressure
chamber of the gas pump and the suction chamber remains

BLOWING ENGINES. 91

open for a longer period ; the discharge into the power
cylinder commencing later, and in lesser volume, the quality
of the mixture remaining always uniform. This retardation
is obtained by governing the gas slide valve similar to the
governing of a locomotive, a method which is also adopted
for blowing engines,

2. The second arrangement is that a connecting channel
is formed between the pressure chamber of the gas pump
and the suction chamber, the area of which is opened or
closed more or less by a throttle valve operated by the
governor. The discharge of the pump then remains con-
stant, but when this channel is partly opened, some of the
gas from the pressure channel returns into the suction
chamber during the suction stroke, and in the same propor-
tion the gas is replaced in the pressure channel by pure air
from the air pump. When the admission valve to the power
cylinder opens, more pure air is admitted, followed by so
much less combustible mixture, according to the volume of
gas pressed back in the channel, the gas pump having first
to replace this volume before the combustible mixture can
be formed. The governor, therefore, regulates the volume
of gas passing back through the channel, and the volume of
gas replaced by air. The amount of mixture formed there-
fore depends upon the extent of opening of the throttle
valve, according to the position of the governor, and so any
intermediate output between full and no load can be
obtained. The closing of the admission valves E is effected
by a spring. The charge is ignited by mngnetic inductors,
and in order to secure a regular ignition of a charge which
is at one time large and at another small, several igniters are
provided for viz., four — two at each side of the cylinder,
one close to the inlet valve, the other one near the end of
the piston in stroke. The inductors are operated by a small
separate shaft which is driven by gears from the main shaft,
by shifting which the moment of ignition can be accelerated
or delayed according to the gas used without having to
stop the engine. When starting the engine it is further
possible to arrange for the ignition not to take place till
after the dead point which insures the engine starting very
slowly without risk of too early ignition. The engine is

92 AIR COMPRESSORS AND BLOWING ENGINES.

started by an independent compressed air arrangement. For
engines directly coupled with blowing cylinders a pressure
of about 150 Ib. is sufficient; for other engines 90 Ib.
to 1201b. is enough. This is of course of the greatest
importance, as the pressure of the compressed air never
exceeds that of the compression with which the engine
works, viz., from 150 Ib. to 180 Ib. It is therefore absolutely
impossible for the compressed air to get into the power
cylinder when the piston is near its dead point, where the
compression of the charge is at its highest and the ignition
takes place. There is therefore no chance of the ignition
being delayed or failing altogether. The compressed air is
distributed by a slide valve, similar to thoie used in steam
engines, to the left and right hand side of the cylinder;
two cylinder volumes of air are generally sufficient to start
the engine easily. The starting arrangement itself consists
of a small compressor with air vessel, driven preferably by
electro-motor. In engines working with a high compression
of the charge before its ignition, it is of the greatest import-
ance to cool the charge, so as to avoid both too high
compression and too high temperature of combustion. The
surface of the combustion chamber is therefore enlarged by
ribs or by special pockets through which water circulates.
The piston is cooled by water entering through the hollow
piston rod, and water also circulates round the glands of the
valve boxes. In keeping the piston cooler than the cylinder
itself, the expansion of the former is kept within reasonable
limits, and a satisfactory working of the engine is assured.
The cylinder is provided with oil drain valves, acting at the
same time as safety valves. The interior of the cylinder is
kept free from any incrustation. No oil crusts will be
found near the exhaust slots, as the burnt charge is driven
out with considerable force alternately from the right and
left side. The great advantage of such an arrangement is
obvious, considering that in all engines exhausting only from
one side early ignitions and explosions are frequent. The
low temperature of the piston also prevents the evaporation
of the oil at the edges of the slots. The advantages claimed
for this t} pe of gas engine are smallness of size, as steady
running as in a steam engine, absence of exhaust valves,

BLOWING ENGINES.

avoidance of free ignition, and the fact that the mixture of
gases takes place only at the inlet valve. Fig. 69 shows six
indicator diagrams from an engine the diameter of whose
piston is 29Jin., stroke 51 Jin.

-427 U>s. a:

FRONT

342 Uu-i

FRONT.

Mean effective pressure
= 1(5 -2 Ib. per sq. in.

FIG. €9.

BACK.

Mean effective pressure
= 93-9 Ib. per sq. in.

22. Vertical Blast-furnace Blowing Engine, constructed by
the Elsadsischen Maschinenbau-Gesellschaft in Mulhausen.*
This engine is cross compound and condensing, with cranks
at right angles, the blowing cylinders being above the steam.
The leading dimensions are as follow : —

Diameter of H.P. cylinder 1,200 mm. (47'25 in.)

Diameter of L.P. cylinder 1,870 mm. (73'6 in.)

Diameter of blowing cylinders.. 2,000 mm. (787 in.)

Stroke 1,500 mm. (59'1 in.)

Revolutions 25 to 50.

Each steam cylinder is carried by a pair of bored frames,
supported by a cast-iron bed plate, figs. 70, 71. The
bearings are lined with white metal, and the diameter of the
journals is 520 mm. (20'5in.), their length being 840 mm.

* Stahl und Eisen, June 15th, 1899.

94 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. 70.

BLOWING ENGINES.

FIG. 71.

AIR COMPRESSORS AND BLOWING ENGINES.

(33'lin.); the crank pins are 330 mm. diameter (13 in.),
and of the same length. The shaft is hollow, and its internal
diameter is 100 mm. (3*94 in.). The flywheel has a diameter
of 6 metres (236 in.), and weighs about 3G tons. The steam
cylinders have Corliss valves, which can cut oft' between 0
and 60 per cent of the stroke. The governor controls the
cut-off in both cylinders, in order to equalise their power.

FIG. 72.

The steam cylinders and their ends are jacketed. All four
pistons are of cast steel, and have packing rings in two
parts. The engine can, if necessary, be started by admitting
steam direct to the low-pressure cylinder. The distance
pieces between steam and blowing cylinders are arranged to
allow access to the stuffing boxes. It will be seen in figs.
70, 71, that the steam piston, with cylinder cover and
blowing cylinder bottom, can be drawn upwards through the
latter cylinder, or, by taking off the covers, the pistons can
be examined. In figs. 72 — 75 are shown the blowing cylinder

BLOWING ENGINES. 97

and valves to a larger scale. These valves permit of high
piston speeds without lessening the volumetric efficiency by
an increase of the clearance ; they are also easily accessible
and removable. Suction valves are shown in fig. 73, and
discharge in fig. 75. As seen in fig. 74, about a third of the
circumference is given up to the discharge and the remainder
to the suction valves. They consist of discs A of steel plate
upon a central spindle B, which is fitted in a cast-iron frame
which has the cross section shown at S S, and forms the
valve seats. Each frame has four spindles — see the left of

Fio. 73.

fig. 74 — and each spindle carries five valves. Above each
valve is a spiral spring R, which rests upon the valve
beneath, and fits into a hollow space in the seat above. Each
frame is held in place by a metal ring E, which is fastened
by screws F F. The wear of valves and spindles is small,
repairs are easily effected, and a high speed is possible owing
to the small stroke of the valves. The piston area is 7^
times the suction- valve area, and 12 J times that of the dis-
charge. At 50 revolutions the velocity through the suction
valves is 19 m. (62'2ffc.) per second, and 31 m. (101-5 ft >
per second through the discharge valves.
SAC

98 AIK COMPKESSORS AND BLOWING ENGINES.

FIG. 74.

FIG. 75.

BLOWING ENGINES.

23. Vertical Compound Blowing Engine, constructed by
the LiltieshalL Company, of Oakengates, Shropshire, for the
Priors Lee Works. — This engine is of the compound vertical

Fio.

type, the blowing cylinders being above the steam. The
steam pressure is 100 lb., the air pressure 10 Ib. to 15 Ib.
per square inch, and they will deliver at 45 revolutions, their
normal speed, 41,500 cubic feet of air per minute. They

100

AIR COMPRESSORS AND BLOWING ENGINES.

can and have run at 60 revolutions. The steam -cylinders
are 42 in. and 70 in. diameter, while the blowing cylinders are
95 in., with a stroke of 5 ft. The steam-valve gear is of the
Corliss type, there being two eccentrics, one for working the
steam and the other the exhaust, for each cylinder. The
air pump is single-acting, 38 in. diameter and 36 in. stroke,
and is driven from the low-pressure piston rod by lever and
links. The crank shaft is of forged steel, the pins being
cast in one with the cranks, and having a diameter and

length of 12 in. The crank journals are 18 in. diameter and
30 in. long ; the body of the shaft is 19 J in. diameter and the
flywheel seat 21 Jin. The flywheel is 20ft. diameter and
weighs about 40 tons. The engine is specially interesting, be-
cause of the valve gear of the blowing cylinders, which en-
ables it to run at such a high speed. The inlet valves are
Kennedy's patent, and the discharge Reynolds'. The manner
in which they are worked is shown in figs. 76 and 77, for
which we are indebted to the Lillieshall Company. In the
latter, D is a lever pivoted near the lower end of the cylinder
and oscillated by an eccentric on the crank shaft. A connect-
ing rod transmits its motion to the right end of the lever B,
whose shaft operates the lever A that works Kennedy's

BLOWING ENGINES. 101

inlet valve. It will be seen from fig. 76 that this is a trunk
passing through but not moving with the blowing piston,
which has two rods, one in front and one behind it, neither
of which are shown in the figure. Ports are cut spirally
in each end of this trunk, and admit the air at the right
moment, cutting off at the end of the stroke. In the figure,
the piston is moving down and the upper ports are admitting
air, and it will be seen that three springs prevent leakage at
the cylinder covers and the piston. A link connects the
left end of lever B with the crank of the left-hand shaft,
fig. 77. This shaft works the delivery valves, two at each
end of the cylinder, by means of arms having toothed sectors
on their ends. The upper valves are closed and are kept to
their seats by the air pressure, and when the piston rises
it will not rise until the pressure in the cylinder has reached
that in the discharge ; but near the end of the stroke the
piston whose spindle is actuated by the toothed sector will
bring it close to its seat, so that it will close without shock.

24. Compound Blast-furnace Blowing Engine, constructed
by Messrs. Davy Bros., of Sheffield.* — Fig. 78 is a sectional
elevation through the low-pressure steam and one of the
blowing cylinders. The steam cylinder is above the blowing
cylinder, an unusual arrangement. The diameters of the
steam cylinders are 48 in. and 84 in., and those of the
blowing cylinders 84 in. The stroke is 54 in., the greatest
possible with the very limited height of the engine-house.
Had it not been for this a stroke of 6 ft. would have been
preferred. The steam cylinders are designed for a 121b.
blast, but 151b. can be obtained if necessary, the steam
pressure being 75 Ib. The maximum speed is 50 revolutions,
and the capacity of the cylinders is then 34,632 cubic feet
of air per minute. Both high and low pressure cylinders
have piston valves with internal expansion valves ; the high-
pressure cylinder has one and the low-pressure two valves,
all of the same size. The expansion valves are adjustable
by hand from the level of the floor. The steam pistons are
conical, and are fitted with Mather and Platt's packing rings
and springs. The air pistons are fitted with junk rings and

* Engineering, March 17, 1899.

102

AIR COMPRESSORS AND BLOWING ENGINES.

an improved form of metallic packing. The clearance is
little more than 3 '6 per cent of the cylinder volume, which
is very good considering the comparatively short stroke.

FIG. 78.

The inlet valves are on the cylinder ends, and the discharge
.valves are arranged circumferentially round the top and
bottom of the cylinders. The valves are of leather, and

BLOWING ENGINES. 103

the area through the inlet valves is a little more than one-
fifth of the cylinder area, so that the suction line very nearly
coincides with the atmospheric. The crank shaft is of steel,
with a diameter of 18 in.; the cranks are 120 de^r. apart, so
that the engine can be started in any position, and it may be
remarked here that an arrangement such as this gives a
more uniform turning moment, and therefore a lighter fly-
wheel can be used. The weight of the flywheel is 35 tons,
and its diameter 16 ft.

25. Vertical Blowing Engine, by ike same firm. — Figs. 79,
80, 81, for which we are indebted to Messrs. Davy Bros.,
show a front and two side elevations of this engine. It was-
built for the Acklan Works of the North-Eastern Steel
Company, and another is in course of construction. The
steam cylinders are above the two blowing cylinders, the
former having diameters of 48 in. and 90 in., the latter being
90 in. diameter. The stroke is 72 in. At 50 revolutions, 70 Ib.
steam pressure, and lOlb. vacuum the engine will deliver
50,000 cubic feet of air per minute. It is constructed for
a steam pressure of 100 Ib. and a corresponding increase of
blast pressure. At this pressure it will indicate 3,800 horse
power.

The steam cylinders are fitted with double-ported Corliss
valves, the cut-off being controlled by a high-speed spring-
governor, which is driven by friction gear. The speed of
the engine can be regulated from 20 to 50 revolutions per
minute by means of a small hand wheel, which controls
the ratio of gear between the engine crank shaft and the
governor. As shown in fig. 80 each cylinder has two eccen-
trics. One of these drives the exhaust valves by means of
a wrist plate, and the other actuates the steam valve. This
permits of a cut-off from the beginning to nearly the end of
the stroke, which is not possible when only one eccentric
drives both valves. The opening and closing of the exhaust
valves is very rapid, and when once closed they remain
almost stationary upon their seats until they are opened
again. This is effected by the arrangement of the arms of
the wrist plate, the connecting links, and valve levers. By
this means the work wasted by valve friction, and the con-
sequent wear, are reduced to a minimum.. The steam valves

104

AIR COMPRESSORS AND BLOWING ENGINES.

are closed by means of small steam cylinders, in place of the
usual spiral springs, which are more or less liable to break,

FIG. 79.

sometimes with disastrous results. The engine is fitted with
a starting valve, and will start from any position against the
full blast pressure. The cranks are at 120 deg., as in the

BLOWING ENGINES.

105

last engine described. The air cylinders are fitted with
mild steel disc suction and delivery valves. These are

FIG. SO.

shown in fig. 82, which is a sectional elevation of the blow-
ing cylinder, whose thickness is 2 in. There are 24 suction
and 24 delivery valves at each end, of 10 in. diameter. The

106

AIR COMPRESSORS AND BLOWING ENGINES.

piston has two packing rings, and there is a space between
the piston and the rings which is filled with elastic asbestos

FIG. 81.

packing, the whole being secured in place by a junk ring in
six segments. By this arrangement the whole of the packing
can be. withdrawn through a small manhole in the top cover

BLOWING ENGINES.

107

of each air cylinder. The A frames that carry the cylinders
are 2 in. thick.

The rigidity and construction of the bed-plate is such that
the engine would not be thrown out of truth even if a con-

=3 '" "

FIG. 82.

siderable settlement of the foundation took place. This is
of importance, as the ground is of a very boggy nature. It
is of box section, 4 ft. deep, 2 in. general thickness, increased
to 3 in. at the crank-shaft pedestals.. The crank shaft is of
forged Siemens steel. The journals are 20 in. diameter and

108

AIR COMPRESSORS AND BLOWING ENGINES.

3 ft. long; the crank pin is 12 in. diameter and 15 in. long.
The diameter of the shaft at the flywheel is 25 in., and the
length of the boss of the flywheel 27 in. The flywheel is
20 ft. diameter and weighs about 40 tons, one half of the
rim being hollow to balance the moving parts. The steam
piston rods are 7J in. diameter, and the blowing piston rods

Fio. 83.

S^ in. The diameter at the small end of the connecting rod
is 8f in., and at the large end 10 in. The upper end of the
connecting rod is forked and has T ends, caps, and brasses.
Each end of the crosshead gudgeon is 8J in. diameter, and
the same length. There are two guide blocks, 24 in. by 12 in.
The centres of cylinders are 1 5 ft. apart. The whole engine
weighs about 400 tons. A test of these engines, with indi-
cator diagrams, will be given later.

BLOWING ENGINES.

26. Blast-furnace Blowing Engine, constructed by the
Kolnische Maschinenbau-Actien-Gesellschaft, of Kdln-Bayen-
thal. — Figs. 83, 84, 85 show a sectional front elevation, a
side elevation, and a plan in section through the valve
passages of the cylinder of a vertical blowing engine whose
leading dimensions are —

Diameter of high-pressure cylinder. 1,600 mm. (63 in.)
Diameter of low-pressure cylinder.. 2,350 mm. (92*5 in.)
Diameter of each blowing cylinder. 2,400 mm. (94-5 in.)
Stroke 1,800 mm. (70 8 in.)

Fia. 84.

The valves of the blowing cylinders are of the same type as
those in the last engine. From the delivery valves the air
passes into ring-shaped passages, whose section gradually
increases to a rectangular discharge of 300 mm. by 1,510 mm.
(11-82 in. by 59'5 in.). Both cylinders deliver into a cylin-
drical receiver of about 1,700 mm. diameter and 3,000 mm.

110

AIR COMPRESSORS AND BLOWING ENGINES.

length (67 in. and 118'2 in.), whose discharge pipe is 900 mm.
diameter (35 J in.). Both steam cylinders have piston valves,
in which work expansion valves ; the diameter of the high-
pressure valve is 840 mm. (33 •! in.), and that of the low-
pressure 1,230 mm. (48J in.). The diameter of the crank
shaft journals is 750 mm. (29J in.), and the length 1,100 mm.
(43'4 in.) ; at the flywheel the diameter of shaft is 850 mm.
{33 '5 in.). The cranks are overhung, and the crank pins

FIG. 85.

are 450 mm. diameter (17f in.) and 510 mm. long (20'1 in.).
The diameter of the piston rods is 250 mm. (9 '85 in.), as
also that of the tail rods ; at the small end of the connecting
rods the diameter is 250 mm., and at the large end 350 mm.
(13'Sin.). The length of the connecting rod is 4,000 mm.
(158 in.), and the distance between centres of cylinders is
6,500 mm. (256*5 in.). The diameter of the flywheel^
8,000 mm. (315 in.), its rim is 360 mm. broad (14*2 in.), and
its radial depth is 420 rnm. (16J in.). The normal discharge
of this engine is 1,600 cubic metres per minute, or 56,500

BLOWING ENGINES. Ill

cubic feet, and its maximum output 1,920 cubic metres, or
67,750 cubic feet of free air. The normal pressure is 1
atmosphere, which may be raised to 1*8. The corresponding
revolutions are 50 and 60 per minute. The boiler pressure
is 6J atmospheres, about 95 lb., and the engine is condensing.
27. On the Efficiency of Blast-furnace Blowing Engines. —
If we assume a mechanical efficiency of 85 per cent, and
calculate the air efficiency by the formula

2 -3 log £

we obtain for the three exponents

n = 1-25 1-3 1408

r?3 - -967 -952 -94

if £ - 1-5,

P-2

and multiplying these by the mechanical efficiency of 85 per
cent, we get the three values 82*25, 81, and 80 per cent as
the total efficiency. The above, however, neglects the fall
of the suction line and the rise of the discharge line due to
valve resistance. The following examples are taken from
"Die Geblase," by Von Jhering, Table L, p. 84, in which
the dimensions, power, and delivery of a number of blast
furnace and Bessemer blowing engines are given : —

Cubic feet per minute 12,000 17,900 28,900 31,700
Absolute pressure of

air in atmospheres... 1'4 1'33 1*41 1*43

Indicated horse power 532 453 770 867

Total efficiency per cent 48'5 72'1 82'6 83'6

These last are calculated as follows : —
The useful horse power

144 p9 v.2 hyp. log —

U = - V*

33000

112 AIR COMPRESSORS AND BLOWING ENGINES.

where v2 = cubic feet per minute, p1 =. absolute pressure of
compression, and p^ = 14*7 Ib.
In the first case

TT _ 144 x 147 x 12000 x 2-3 x log- 1-4 _
33000

Hence the total efficiency

258

ift = -— = 4b'5 per cent.
5o2

This is certainly below what could be obtained from this
engine. The average of the four results is 71*7, and is
probably very near what we might expect from a blowing
engine. We have already obtained an efficiency of 69 per
cent for one of these engines in Section 16. The following-
figures are obtained from the above-mentioned work, and are
from a test made with a beam engine. The indicated horse
power was 332, that done in the blowing cylinder 281-3,
so that the mechanical efficiency was nearly 85 per cent
(including the work done on the feed pumps, 88 per cent).
The piston area was 6 '38 square metres, and the piston
speed 1'1678 metres per second, so that the number of cubic
feet swept out by the piston per minute was 15,800. The
pressure to which the air was compressed was 1'304 atmo-
spheres absolute, and if we assume the volumetric efficiency
to be unity, the useful horse power was

U - 144 x U'7 X 158°° X 2'3 X log 1>3Q4
33UUO

giving an air efficiency of

7/3 = 28
and a total efficiency of

7/3 = = 95'6 per cent»

7h = ^ = 81 per cent.

Fig. 86 shows the indicator diagrams of the steam cylin-
ders, and fig. 87 those of the blowing cylinders, of the large

BLOWING ENGINES.

113

compound condensing blowing engine described in Section 25.
The diameters of the steam cylinders are 48 in. and 90 in.,
and those of the blowing cylinders are 90 in., the stroke

High-pressure Side.

Low-pressure Side.

STEAM CYLINDERS TOP

STEAM CYLINDERS BOTTOM

FlG. 36.

being 72 in. The diagrams were taken on November 25th,
1900. The steam pressure in the engine-house was 76 Ib.
by gauge, the vacuum 19 in., and the speed 35 revolutions.

High-pressure Side.

, AIR CYLINDERS TOP

Low-pressure Side.

AIR C YL INDERS BOTTOM

FIG. 87.

The greatest pressure in the high-pressure cylinder was
66 Ib. above the atmosphere. The peculiar shape of the
discharge lines on the air diagrams is due to the fact that

9AC

114 AIR COMPRESSORS AND BLOWING ENGINES.

other engines were pumping into the air mains at the same
time. We find from the diagrams —

High-pressure cylinder, M.E.P. 41 '7 5,

Indicated horse power ..................... 960

Low-pressure cylinder, M.E.P. 9 '2 15,

Indicated horse power ..................... 746

Two blowing cylinders, M.E.P. 971,

Indicated horse power of both ......... 1,570

This gives a mechanical efficiency of 92 per cent. The ideal
horse power required to compress isothermally is obtained
as follows. Measurement from the diagrams shows that the
volumetric efficiency is 96*75 per cent, and the mean pres-
sure at the end of the four strokes is 12 Ib. above the
atmosphere. Assuming this as the mean pressure to which
the air is compressed, the ideal horse power is —

9A-7

14-7 x -7854 x 902 x 6 x 70 x hyp.log "--'
U- 9675x2 x-

= 1365.
The air efficiency is therefore

87 per cent'

and the total efficiency is

7/1 = IS = 8° per °ent

The engines are fitted with Crewe and Davy's patent radial
trip gear, which enables steam to be cut off from the com-
mencement to nearly the end of the stroke, so that con-
siderably more power can be obtained. Such gear as this is
of the utmost importance in case an extra pressure of blast
is required, which is generally the case when the steam
pressure is at its lowest.

28. Bessemer Blowing Engines. — These engines work at
a higher pressure than those for blast furnaces. The pres-
sure above the atmosphere is from 22 Ib. to 30 Ib., or about

BLOWING ENGINES. 115

1 J to 2 atmospheres. The following is a test of one of these
engines, whose leading dimensions are —

Diameter of steam cylinder 1,255 mm. (49*4 in.)

Diameter of blowing cylinder 1,410 mm. (55*6 in.)

Stroke 1,410 mm.

The speed was 40 revolutions, and the suction pressure
13 '8 Ib. per square inch. The indicator diagram shows that
9 5 '3 per cent of the cylinder volume was filled with fresh
air each stroke at this pressure, so that the volumetric
efficiency

-,y3 = 95 '3 x = 89 '7 per cent.

The indicated horse power from the blowing cylinders
was 1,010, and that of the steam cylinders 1,152. The
mechanical efficiency was therefore 87 '6 per cent. The abso-
lute pressure to which the air was compressed was 46 '3 Ib.,
and ideal horse power necessary was —

144^v, hyp. log^-1

"33000

_ 2 x 14-7 x -897 x 7854 x (55'6)3 x 80 x 2'3 log 3-15 _ g95
12 x 33000

so that the total efficiency

and the air efficiency

825 Q1 7,

= 81*75 per cent.

825 71 R
>h == ~ = percent,

Measurements from the diagram show that the fresh
volume of air drawn in per stroke was 2 '462 times its
volume when compressed from 13'81b. to 46- 3 Ib. absolute,
hence the exponent of compression

„ = !?gi<LLJ«Lls* = 1-345.

log 2-462

116 AIR COMPRESSORS AND BLOWING ENGINES.

Messrs. Breitfeld, Danek, and Co., of Prag-Karolinenthal,
have kindly supplied me with five sets of diagrams of a
Bessemer blowing engine. The leading dimensions are —

High-pressure cylinder diameter 950 mm.

Low-pressure cylinder diameter 1,400 mm.

Blowing cylinder diameter 1,350 mm.

Stroke 1,500 mm.

Revolutions 50

The fifth set give the following results : —

Indicated horse power of steam cylinders. . . 1,340

Mean pressure of blowing cylinders : . . . 1 8 '37 Ib.

Horse power of both 1,220

Mechanical efficiency 9 1 '1 per cent.

The mean discharge pressure \yas 3 '14 atmospheres abso-
lute, and the volumetric efficiency 86 per cent. The mean
pressure with isothermal compression for this is 14'4 Ib.
This gives

14-4 „„
r/., = •— - - = fo'4 per cent,

LO'OI

and the total efficiency is

^ = 78-4 x '911^ = 71'3 per cent.

29. Bessemer Bloivintf Engine, constructed l>y the Kolnische
Maschinenbau-Actien-Gesell&chaft, of Koln-Bayenthal. — Fig.
88 is an elevation, fig. 89 a sectional plan, fig. 90 a complete
plan, and fig. 91 an end elevation partly in section of the
blowing cylinder of a horizontal engine. The leading dimen-
sions of the engine are —

High-pressure cylinder diameter ... 1,300 mm. (5T2 in.)

Low-pressure cylinder diameter ... 2,000 mm. (78'S in.)

Diameter of each blowing cylinder. 1,800 mm. (71 in.)

Stroke 1,700 mm. (67 in.)

The blowing pistons are, as usual, driven from the tail rods
of the steam pistons. The valves are set in two rings at the
ends of each cylinder, the valves themselves being shown in

BLOWING ENGINES.

117

FIG.

FIG. 89.

118

AIR COMPRESSORS AND BLOWING ENGINES.

fig. 92. Each valve seat holds four delivery or four suction
valves, the former being nearer the cylinder ends, and dis-
charging into a passage of rectangular section whose breadth
radially increases from the bottom to the top, see fig. 91.
The valves are pressed on their seats by spiral springs, and
the valve seats are held to the casting by a central bolt. In
fig. 92 the lower valves are the discharge and the upper the
suction. The latter draw their air from a passage in the
engine foundation, which communicates with the outer air ;

such passages usually terminate in a chimney, so that the
air supplied to the cylinder is as cold and free from dust as
possible. The ring-shaped discharge passages terminate in
two rectangiilar openings 1,000 mm. by 240 mm. (39*4 in. by
9*45 in.), which are connected by a bent pipe of rectangular
section to the discharge pipe of 550 mm. (21-7 in.) diameter,
figs. 88 and 89. Fig. 91 gives an end view in the right
hand upper quadrant ; a section through the cylinder pas-
sages in the left hand upper quadrant ; beneath this a view
of the valve chest from the suction side ; and in the remain-
ing quadrant a section through the discharge passage. The

BLOWING ENGINES.

119

steam valves are piston valves of 410 mm. and 800 mm.
diameter (16*5 in. and 31 '5 in.), with valve rods of 70 mm.
and 100mm. diameter (2'76 in. and 3*94 in.); the former
has a variable cut off. There are three guide blocks to each
piston rod : one on the tail rod of the blowing- cylinder, the
second between the two cylinders, arid the third at the
crosshead. The piston rods are 250 mm. diameter (9 '84 in.),

FIG. 91.

and the connecting rods have diameters of 220 mm. and
270 mm. (8 '65 in. and 10'6 in.) at small and large ends, and
their length is 4,250 mm. (167J in.) The distance between
the centres of cylinders is 5,400 mm. (2 12 '5 in.). The
crank pin diameter and length are 400 mm. (1575 in.),
those of the crank journals 600 mm. and 750 mm. (23 -6 in.
and 29*5 in.), and the diameter of the crank shaft at the
flywheel is 700 mm. (27 '6 in.). The diameter of the flywheel

120

AIR COMPRESSORS AND BLOWING ENGINES.

is 8,000 mm. (315 in.), the breadth of its rim 340 mm.
(13'4 in.), and radial depth 435 mm. (17'lin.); there are
eight arms.

30. Vertical Compound Bessemer Blowing Engine, con-
structed by Messrs. Schneider and Co., Creusot, for the

FIG. 92.

/Societe des Acieries de Longwy* — This engine has the
following leading dimensions : —

Diameter of high-pressure cylinder.

Diameter of low-pressure cylinder.

Diameter of each blowing cylinder.

Stroke

Capacity per minute

Pressure above the atmosphere ...

Initial pressure upon the piston ...

Revolutions per minute

1,200 mm. (47J in.)
1,700 mm. (67 in.)
1,400 mm. (55'1 in.)
1,400 mm. (55'1 in.)
400 c.m. (14,100 c. ft.)
29-4 Ib. per sq. in.
78 Ib. per sq. in.
50.

* " Appareils de Compression d'Air," from the Bulletin de la Societe de 1'Indus-
trie Minerale, Tome VII.

BLOWING ENGINES.

121

The indicated horse power was estimated at 1,400. and the
consumption of steam at 14'31b. per indicated horse power

FIG. 98.

hour. There are two cranks at right angles ; the blowing
cylinders are placed above the steam ; the steam valves are
of the Corliss type, the steam valves having trip gear for the

122

AIR COMPRESSORS AND BLOWING ENGINES.

high-pressure cylinder, but not for the low, in which the
point of cut-oft' is fixed. The governor is so constructed
that the speed can be varied as required. Fig. 93 shows a
sectional elevation through the piston, liner, cylinder, and valve

FIG. 94.

chest of the blowing cylinder, the valves not being shown in
place. The blowing piston is at the bottom of the stroke.
The cylinder is water jacketed. The air valves are self-
acting, and are in sufficient number to reduce the velocity
of the air through them to 82 ft. a second at 50 revolutions.

AIR COMPRESSORS. 123

This type of valve is used by Messrs. Schneider and Co. for
all powers and pressures, and works very well. Fig. 94
shows a sectional elevation and plan of the valve complete.
The valve itself is a copper plate 62 mm. (2'44 in.) external
diameter and 25 mm. (1 in.) internal, and 1 J mm. ('05 in.)
thick. The spring is also of copper, and the valve seat and
valve guard of bronze. The spring is compressed to
20-75 mm. ('817 in.) when the valve is closed. The guard
permits the valve to rise 5 mm. ('195 in.), and the cylindrical
area at the outer circumference of the valve is therefore
9 '7 sq. cm., or 1J sq. in. Messrs. Schneider give the area
as 8'9 sq. cm., corresponding to a rise of 4'6mm. ('18 in.).
Just under the valve plate the passage has internal diameters
of 54 mm. and 32 mm. (2'1 in. and 1'25 in ), and there are
four ribs 3| mm. (*136m.) thick, which make the area of
the passage 13 '3 sq. cm., or 2 '06 sq. in. The engine can
work condensing or non-condensing, valves being fitted for
that purpose in the exhaust pipes. The condensers and air
pumps are in a pit at the back of the engine, fig. 95, in order
that the jet may be drawn in by the vacuum alone. There
are two vertical single-acting air pumps, driven by levers
actuated by the crossheads of the piston rods. One pump
is sufficient even at full speed.

CHAPTER V.
AIR COMPRESSORS.

31. These may be divided into single acting and double
acting, or those that deliver dry air, have water injected into
their cylinders, or a mass of water in the cylinder moving
to and fro with the piston. But as the valves are the most
important feature of the compressing cylinder, the best
division is into those which have self-acting or mechanically-
controlled valves. The former have the advantage of
simplicity, and their first cost is consequently less ; the latter
are more durable, give less trouble, and allow a higher
piston speed than the former. Self-acting valves are

124 AIR COMPRESSORS AND BLOWING ENGINES.

Fi<J. 95.

AIH COMPRESSORS. 125

usually closed by difference of pressure and a spring-, and
opened by difference of pressure opposed by the spring ;
mechanically-controlled valves are opened by difference of
pressure, and usually have a dashpot to prevent shock in
opening, but mechanical means are used to bring them close
to their seats shortly before it is necessary for them to close,
which they do by difference of pressure at the right moment
without shock. They can therefore be made large, and
given a considerable lift.

Reciprocating or oscillating valves, the latter, for example,
of the Corliss type, may be used as in blowing engines for
the admission of air, because they close at the end of the
stroke; and the moment of admission, i.e., when the com-
pressed air in the clearance has expanded to atmospheric
pressure, can be approximately determined. They may
also be -used for the discharge valve, closing at the end of
the stroke, but as the point when discharge commences
depends on the ratio of compression, they must either be
opened by mechanical means depending on difference of
pressure, or there must be an additional discharge valve
which prevents the return of air from the pressure pipes
into the cylinder.

32. Suction and delivery valves for a compressor con-
structed by the Friedrich Wilhelms-Hutte, of Mulheim^
a.d. Ruhr. — There are two air and two steam cylinders,
the diameter of the former being 625 mm. (24'6in.), and
of the latter 700 mm. (27 ;6 in.), with a stroke of 1,000 mm.
(39 '4 in.). The air compressing pistons are driven direct
from the steam pistons, the crank shaft and flywheel being
on the other side of the steam cylinders ; the cranks are at
right angles. There are three delivery, and five suction
valves in each cylinder end, which is divided into two
halves by a .vertical diameter, the delivery valves being
placed on one side of this, and the suction on the other. A
delivery valve is shown in sectional elevation in fig. 96, and
in end view in fig. 97. The passage in the valve seat is
90mm. (3'55 in.) diameter, so that the discharge area is
0'062 of the piston area. The seat is of bronze, and the
conical valve of 100 mm. (3'94 in.) diameter, of delta metal.
It has a hollow guide spindle of 43 mm. (1*69 in.) diameter,

126 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. 96.

Fio. 97.

AIK COMPRESSORS.

127

in which is a spiral spring of steel of 22 mm. external
diameter ('867 in.), and 2 mm. diameter wire. The guide

FIG. 98.

FIG. 99.

spindle .carries a piston of delta metal at its outer end,
which works in a dashpot. The piston is 91 mm. diameter
(3 '59 in.), and the cylinder in which it works 92 mm.

128 AIR COMPRESSORS AND BLOWING ENGINES.

(3 -6 2 in.), so that the air can pass round its circumference.
The spring is held at its outer half in a bronze cylinder of
28 mm. (I'l in.) diameter, the inner diameter of the valve
guide being 28J mm. The dashpot, of course, prevents
shock, with consequent noise and damage to the valve when
the valve is opening and closing. Fig. 97 is an end view
with the dashpot cover removed. Fig. 98 is the suction
valve, which is of delta metal, the seat being of gun metal, the
diameter being 80 mni., so that the suction area is 0'082 of
the section of the cylinder. The valve spindle is 16mm.
('63 in.) diameter, and a piston is screwed upon its outer
end, working in a dashpot. The diameter of piston and
dashpot is 60mm. (2*36 in.) diameter, and the valve is
pressed on its seat by a spring of steel 24 mm. external
diameter ('945 in.) of 3 mm. wire. Fig. 99 is a sectional
end view through the middle of the spindle.

33. Compressor constructed ~by the, Tilghman's Patent
Sand Blast Company. — Sections through the cylinder are
shown in figs. 102 and 103, and the construction of the valves
is illustrated in figs. 100, 101, the former showing the parts of
the inlet valve, and the latter those of the delivery. As
the inlet valves are practically inside the cylinder, the

FIG. 100.

clearance space required to admit them to a
determines the ultimate volumetric efficiency of the com-
pressor. Matthewson's patent valves occupy very small
space in proportion to their areas, and the clearance is only
1 to 2 per cent of the cylinder capacity. They are exceed-
ingly light (a 3 in. valve and spring scaling less than two
ounces), perfectly air-tight, and practically noiseless in

All? COMPRESSORS. 129

working. Both valve and spring are made from a special
quality of sheet steel, the valve being ground on the contact
side whilst held by a magnetic chuck. The delivery valve is
a light steel stamping held on its seat by a special close
coil spring, which, when the valve has attained the required
lift, is completely closed, thus avoiding the shock caused by
a fixed stop. The efficiency of this design is amply proved
by their long life and by the absence of noise when working.
The cylinders are fitted with cast-iron liners of a special
mixture, the space between liner and shell forming the water
jacket. The cylinder ends are perfectly flush, and as guards
are fitted to the inlet valves, nothing can possibly find its
way into the cylinder.

The air openings through these guards have sufficient area
to allow the gas to pass freely through them. Regarding water
jacketing, it is claimed that greater efficiency is obtained by
utilising the cylinder ends as valve chests than by using
radial valves and water jacketing the cylinder ends, as the

FIG. 101.

increased valve area and reduced clearance more than
compensate for any extra cooling obtained. When it is
considered that with compressors ranging from 20 to 1,000
cubic feet of free air per minute a single stroke only occupies
Yo-th to ith of a second, it cannot be expected that much
cooling will take place in the cylinder. Volumetric efficiencies
of 90 and 80 per cent are guaranteed with compound and
single-stage compressors respectively, working up to a
pressure of 100 Ib. for the former and 80 Ib. for the latter.
A patent governing inlet valve is fitted, which automatically

10AC

133 AIR COMPRESSORS AND BLOWING ENGINES.

WATER INLET

FIG. 102.

fis

FIG 103.

AIR COMPRESSORS.

131

132

AIR COMPRESSORS AND BLOWING ENGINES.

regulates the amount of air compressed to that required
(see figs. 102 and 103). When the amount of air required is-
less than the capacity of the compressor the air pressure
rises, and, by means of a small weighted piston, air is
admitted from the air receiver to the regulator cylinder,
thus closing the air inlet, and thereby putting the piston or
pistons into equilibrium by causing a partial vacuum on

FIG. 106.

both sides. The power saved by its use is considerable
where there are frequent variations in the amount of air
used.

34. Vertical Compound, Air Compressor, constructed l>y
Messrs. Duncan, Stewart, and Company, Glasgow. — The
machine has steam cylinders 12 and 24 in. diameter, and air
cylinders 13 and 22, the stroke being 12 in. The steam
cylinders are supported at the back by strong cast-iron
columns, and at the front by steel columns. The whole
structure is mounted on a bedplate of cast iron ; the crank
shaft is of mild steel, with crauks at right angles and
webs forged solid. Both steam cylinders are fitted with
Meyer's valve gear. Each piston rod is in one forging.

AIR COMPRESSORS.

133

Fm. 107.

134 AIR COMPRESSORS AND BLOWING ENGINES.

Three views of the engine, for which we are indebted to
Messrs. Duncan, Stewart, and Co., are shown in figs. 104,
105, and 106, and fig. 107 is a section of the high-pressure
air-cylinder, from which it may be seen that the valves
are placed in the covers at top and bottom. The moving
parts of the valves are of manganese bronze, and are held
in position by springs whose tension is adjustable. The
valve seats and guards are of best phosphor brcnze, and
grids are placed above and below the valves in the lower
and upper covers to prevent their falling or being drawn
into the cylinder. Each cylinder is surrounded by a water
jacket, and there is also a tubular cooler between the
cylinders, fig. 106. The air inlet valve on the low-pressure
cylinder has an automatic adjustment for controlling the
volume of air passing according to the amount required.
The steam pressure is 120 lb., and the air 100 Ib. When
running at 100 revolutions, the capacity is 400 cubic feet
per minute.

35. The Rryszat Air Compressor. — Messrs. ScV after and
Budenberg have kindly sent us a description of this com-
pressor, which is shown in fig. 108, a section of the cylinder
being given in 109. In this system the suction and
pressure valves are compactly arranged one within the
other, and they form the actual cylincUr end. Both valves
are of the same diameter as the piston itself, their lift is
very small, and there is no clearance whatever between
piston and valves. It can be run at a high speed, and
there is no loss through clearance space. Water cooling
can in many cases be dispensed with, as the valves offer a
large cooling surface for the compressed air. There are no
stuffing-boxes nor crosshead.

In fig. 109, a is the suction valve, and b the pressure
or delivery valve, which latter is carried by a metallic
diaphragm gt which is firmly held at the joint ring c ;
/ shows the spring of the suction valve. The seat of the
suction valve is on the pressure valve, and d represents
the seat of the pressure valve against the end of the
cylinder.

The movement of the pressure valve and diaphragm is
checked by the spring h, and the tension of this spring can

AIR COMPRESSORS.

136

be regulated by the nut /. The air is drawn in by the
central passage, and is discharged by the pipe indicated
by the arrow pointing upwards. The pressure space is

separated from the suction by the pressure valve b and the
diaphrngm g.

It will thus be seen that the valves close tightly upon
the cylinder end, and will open readily when the required

136 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

137

pressures are obtained. The piston may actually touch the
surface of the suction valve, thereby raising the pressure
valve from its seat. When the piston commences the

FIG. 110

return stroke the pressure valve closes, and the air is drawn
in at once.

The flywheel is arranged to form the driving pulley.
The cylinder and bearings are lubricated by ordinary drop

138

AIR, COMPRESSORS AND BLOWING ENGINES.

sight-feed lubricators. Ring lubrication is employed in the
main beatings of the crank shaft. When required for
pressures not exceeding 1201b. per square inch, water
cooling can be dispensed with, provided the compressor is
required to work for short periods only at frequent intervals,
and not continuously. For continuous working it is prefer-
able to employ water cooling, even at lower pressures.

These compressors can be used for gases as well as air.
They have hitherto been made in two sizes, with 4 in. and
6 in. diameters of piston respectively, but larger sizes can be
supplied if lequired. The stioke of each size is 4 in., and
their capacities in cubic feet per hour 525 and 1,050.

FIG. 111.

36. Compound Air Compressor, constructed by Messrs.
Schuchtermann and Kremer, Dortmund, for the Harpener
Mining Co.* — Figs. 110 to 115 show the air cylinders and
valves. Fig. 110 is a sectional elevation of the low-pressure
cylinder, and fig. Ill -a sectional plan view of the high-
pressure, while figs. 112 and 113 show transverse sections of
both. The engine is cross-compound, the high-pressure air
piston being driven direct from the high-pressure steam

* Engineering, December 12,1902.

AIR COMPRESSORS.

139-

140 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

141

piston, and similarly for the low-pressure. It is calculated
to compress 5,200 cubic metres (183,650 cubic feet) of air
per hour. The leading dimensions are : —

Diameter of low-pressure steam and

air cylinders 900 mm. (35 -43 in.)

Diameter of high-pressure steam and j<

air cylinders 575 mm. (22*63 in.)

Stroke..., 1,100 mm. (43'30 in.)

Flywheel, diameter 5,500 mm. (216-5 in.)

FIG. 114.

142

AIR COMPRESSORS AND BLOWING ENGINES.

The steam pressure is 169 Ib. per square inch, the air
pressure 88 to 1171b. per square inch. There is a tubular
inter cooler (fig. 112), but the air cylinders are not fitted with

FIG. 115.

cold water jackets, nor are they otherwise cooled. The high-
pressure steam cylinder and the intermediate re-heater
underneath the floor level (fig. 113) are steam-jacketed. The

AIR COMPRESSORS. 143

suction and delivery air valves are self-acting, of the Coll-
mann type, and are made of aluminium bronze. Fig. 114 is
a delivery and fig. 115 a suction valve. In this type a spiral
spring closes the valve, an oil piston coming into play at the
last moment to prevent the valve from striking on its seat,
the working being noiseless throughout. The action of the
oil piston can be regulated while the engine is in motion ;
both the valves are easy of access for maintenance and
repair. The piston is immersed in oil, which almost reaches
the upper part of its neck-shaped extension. This remains
uncovered for regulating purposes. The oil flows from one
side of the piston to the other through grooved ports cut in
the wall of the bush in which the piston works, and these,
according to the position of the piston in the bush afford a
larger or smaller area open to the flow of the oil. Just
before the valve touches its seat its downward motion is
retarded by the piston, which has reached a point of its
stroke at which the space open to the flow of the oil is very
small. This ensures the noiseless closing of the valve. The
above action can be easily adjusted by altering the position
of the piston relative to the ports, either by moving the
piston or the bush, the latter being the easier. The oil
piston contains a relief valve, which aids the flow on the
upward stroke.

37. Ingersoll Sergeant Compressors. — Fig. 116 is a
longitudinal section through the cylinder of a type of
compressor constructed by the above company. The valves
are of forged steel with a vertical lift, the delivery valves
having springs within them, those on the suction valves
being placed round the valve spindles and pressing upon
collars pinned to their lower ends. The suction valves
being at the bottom of the cylinder, there is no fear of their
being drawn into it and so wrecking the compressor, so that
sieve-like guards, which take up a considerable amount of
heat and warm the incoming air, are unnecessary. The
piston, as it nears the end of the stroke, forces oil upon the
suction valves. The covers and sides are water-jacketed,
but the valves are accessible by removing the caps above
and below them. The compressing piston is driven direct
from the steam piston, fig. 117, a crosshead on the piston

144 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. lie.

FIG. 117.

AIR COMPRESSORS.

145

rod working in guides on either side, having at its ends two
connecting rods which drive overhung cranks keyed on a
shaft with two flywheels on either side of the steam cylinder,
so that the arrangement is very compact. This type is made
in twelve sizes for pressures from 151b. to 80 lb., the
smallest size having steam and air cylinders 6 in. diameter
with 6 in. stroke, and the largest with 12 in. diameter and
12 in. stroke for 80 lb. pressure, but with an air cylinder
diameter of 16 Jin. for 30 lb. pressure.

Fio. 119.

Fio. 118.

Another very successful form of compressor is shown in
sectional elevation in fig. 118, in which the suction valves are
carried by the piston, which is hollow ; the piston rod at the
end furthest from the steam cylinder being hollow and
forming part of the suction pipe, to which it is connected by
a stuffing box. The admission of air being through a single
tube, a constant flow of air is created in one direction, thus
completely filling the cylinder at each stroke with air at
atmospheric pressure, owing to its momentum. The air
inlet valves are large rings G, of very soft homogeneous open-

llAC

146 AIR COMPRESSORS AND BLOWING ENGINES.

hearth steel, made from a solid billet, which is punched and
worked into the required form and size without any welding.
So well do they wear, that the company guarantee them for
five years, and state that they have not had a single case of
breakage of one of these valves, one of which is also shown
in fig. 119. The holes in its sides are for pins, which are
fixed in the piston, and prevent rotation without hindering
the opening and closing of the valve. The inertia of the
valve at the end of the stroke assists its rapid opening and
closing at the right moment. The covers and side of the
cylinder are water-jacketed, and the delivery valves placed
in the covers. The piston is driven from the tail rod of the
steam piston, the flywheel shaft being on the further side of
the steam cylinder.

Amongst several other types, this firm constructs com-
pound compressors, compressing to 100 Ib. The diameters
of the smallest in the order — steam high-pressure cylinder,
steam low-pressure cylinder, air low-pressure cylinder, air
high-pressure cylinder — are 10J in., 18 in., 16Jin., and
lOJin., with a stroke of 30 in. This runs at 90 revolutions,
has a capacity of 6*84 cubic feet of free air per revolution,
and requires 97 I.H.P. to drive it. The largest size has
diameters 24 in., 44 in., 36 Jin., and 22Jin. ; stroke 48 in.,
70 revolutions, 55 cubic feet, and 664 I.H.P. The total
efficiency of this latter, assuming a 100 per cent volumetric
efficiency, is, from equation (7),

ideal horse power
indicated horse power
_ 144 x 14-7 x 55 x 70 x 2-3 log. 7-82

33000 x 664
= 76-4 per cent.

With a volumetric efficiency of 95 per cent this would
become 72*5, in any case a good result.

38. Air Compressor Valves, by Davey, Paxman, and
Co., Colchester. — Figs. 120, 121, 122 show the suction, and
figs. 123, 124, 125, and 126 the delivery valve constructed by
this firm for a cylinder 24J in. diameter and 32 in. stroke.
Fig. 1 20 is a longitudinal section, and at the top a half plan,

AIR COMPRESSORS.

147

of the valve. It will be seen that this is treble-beat, the
outer diameters of the three seats being 6J in., 4J in., and
2 in. The valve is of high carbon steel, and contains eight
passages through which the air that passes the two inner
seats can flow. The valve has a long spindle, which is

FIG. 121.

FIG. 120.

SECTION THRO VALVE SEAT AT A. A

FIG. 122.

guided in a bush of gun metal. Fastened to the end of the
spindle is a cap, against which a spiral spring presses, the
lift of the valve being fixed by a ring of hardened steel, of
dovetail section, held by the cap. When the valves work
horizontally the centre of gravity always remains inside the

148

AIR COMPRESSORS AND BLOWING ENGINES.

guide bush whether the valve is open or shut, so that the
valves never drop when they are open, and are bound to
close fair and true. Fig. 121 is a plan of the valve seat, and
fig. 122 a sectional plan cutting it at about the middle of its

FIG. 123.

FIG. 126.

height. The seat is constructed of cast iron. The delivery
valve is shown in longitudinal section in fig. 1 23. It has
two beats, whose external diameters are 6fin. and 3| in.,

AIR COMPRESSORS.

149

and it contains eight passages through which the air that
passes the inner seat flows. The valve is kept to its seat

by a spiral spring, and the valve spindle is guided by a
bush. When the valve opens a point at the end of the

150

AIR COMPRESSORS AND BLOWING ENGINES.

spindle comes against a small piston of steel, which is acted
upon by a conical spiral spring. The lift is thus limited,
without shock. Fig. 124 shows a section of the valve seat,
and fig. 125 a plan of the face, while fig. 126 is a transverse
section through the middle of the valve spindle.

39. The Reavell Air Compressor.* — Figs. 127 and 128
show two sectional elevations of this four-cylinder com-
pressor, which can be driven by steam belting or electro-
motor. The casing is circular, and the cylinders are
provided with trunk pistons, whose connecting rods are

FIG 129.

actuated by a single crank. It will be seen, figs. 133 and
134, that the connecting rods have only a small bearing on
the crank pin, and are held in place by two keeper rings.
The gudgeon at the piston end is hollow, and has a groove
cut in it, which serves as an admission passage when the
piston is moving towards the centre. The piston is also
shown in figs. 135 and 136, in plan and sectional plan.
There are also suction ports in the cylinders, figs. 130 and
132, which are uncovered when the piston reaches the end

* Engineering, February 16th, 1900.

AIR COMPRESSORS.

FIG. 130.

151

SECTION fHRO £ F

FIG. 181.

152 AIR COMPRESSORS AND BLOWING ENGINES.

Fio. 132.

Fio. 133.

Fio. 134.

AIR COMPRESSORS.

153

of the suction stroke. The air is drawn in to the centre of
the casing through a valve placed at one side, which consists
of a movable and fixed cylinder, the former moving inside
the latter, having radial passages cut in it and being fixed
to a lever, fig. 129, held down by a weight and a spring,
but raised by a small plunger working in an air cylinder at
the other end, which is supplied with air under pressure, so
that if this pressure is in excess of that required the weight
is raited and the passages cut in the cylindrical valve are
closed. A vacuum is thus formed in the centre of the
casing, and the work required to drive the compressor is
very small. The cylinders are water-jacketed, and are
corrugated to increase the cooling surface. They all deliver
into a circular passage around the casing, fig. 128, and ready

FIG. 135.

FIG. 136.

access to the delivery valves can be obtained through the
covers. These valves are of steel and are very light. They
will be shown later in detail in connection with this firm's
four-cylinder compound compressor. They are kept in their
places by light springs, fig. 130. The cylinder cover is
hollow and connected with the water jacket.

40. The Reavell Compound Air Compressor. — This type
of air compressor was formerly constructed by Messrs.
Reavell and Co., of Ipswich. Their latest design is described
on page 159. Fig. 137 shows a sectional elevation through
the axis of the shaft, and fig. 139 one at right angles thereto.
From the latter it will be seen that the crank drives four
connecting rods, and these in turn four pairs of high and low

154

AIR COMPRESSORS AND BLOWING ENGINES.

Alfl COMPRESSORS.

155

pressure guide pistons tandem fashion. The low-pressure
cylinders have no suction valves, but each connecting rod
has two milled out passages, which connect the cylinder
with the space in which the shaft works during its inward or
suction stroke, but on the return stroke are closed. There
are also passages in the cylinder walls, which are opened
just before the end of the stroke, thus ensuring the complete
filling of the cylinder. On its outward or return stroke the
air is compressed until it lifts the discharge valves, and the
air passes into the receiver. All four receivers are connected

Fir.. 139.

together by bent pipes, and as, while one low-pressure piston
is compressing, the opposite high-pressure is drawing in a
charge of air, the air has to travel from one side of the
compressor to the other, and is thus cooled in the bent pipes,
which are surrounded by water. The principal advantage
of compound compression is, of course, that the air can be
cooled in an intermediate receiver. When the small piston
moves inwards air is drawn in through the suction valves at
the side of the end of the cylinder, and on its outward stroke
the air passes through the delivery va-lves in its end into a
pert cast round the periphery of the casing. Three sides of
this port are in contact with the cooli'ig water in the casing

156

AIR COMPRESSORS AND BLOWING ENGINES.

or tank. The valves, one of which is shown in fig. 138, are
of one size in all sizes of compressors, the number being
governed by the requirements of each size of cylinder. Each
valve weighs less than an ounce, the travel is only TVhi.,
and they work noiselessly. With a four-cylinder machine
running at 250 revolutions, there are 1,000 deliveries of- air
per minute, or more than 16 per second. This continuous
stream enables a large reservoir to be dispensed with. The
diameters of the low and high pressure cylinders are 10 in.

Fio. 140.

and 5 in. respectively, so that, as the larger piston is annular,
the ratio of areas is 3 to 1. The stroke of the pistons is
5 in. The air is admitted to the centre of the casing through
the openings at the end and through an automatic inlet
arrangement, figs. 137 and 139, the former giving a vertical
section through the central spindle and the latter one
transverse thereto. The air supply is controlled by this, so
that when no air is required from the compressor the inlet
valve is automatically closed. Referring to rig. 139, it will
be seen that the inlet valve consists of two concentric rings,

AIR COMPRESSORS.

157

of which the inner is movable, while both have passages cut
in them. The inner ring carries a spindle which has
attached to it a weighted lever with a controlling spring.
To the underside of the lever is fastened a small piston rod,
whose piston works inside a cylinder, the underside of which
is in connection with the air delivery pipe. When the

FIG. 141.

compressor is working normally the valve is in the position
shown, so that the ports are open, but when the pressure
exceeds a certain amount the piston raises the lever and
closes the passages. Then, since a vacuum is soon formed
in the suction chamber, the compressor requires very little
work to drive it.

The type of valve fitted is shown in section in fig. 140.
Each cylinder has a suitable number of these valves. These
compressors can be driven singly, or one at each end of the
engine or motor shaft. Fig. 141 is the diagram of torque

158 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS. 159

in the latter case, the dotted lines showing the torque
required by each compressor, and the full line the sum of
these, giving very nearly a uniform resisting moment.

41. Reavell Two-stage Air Compressors, — The latest
design of these compressors, which is intended to supersede
those already described, is shown in perspective in fig. 142.
There is a motor in the centre, the low-pressure cylinder
being on the left and the high-pressure on the right ; between
these is an inter-cooler. Each of these compressors is similar
to the belt-driven single-stage compressor shown in section in
figs. 143 and 144. In fig. 145 a sectional elevation is also
shown of the arrangement of motor and compressor. A con-
tinuous shaft passes through the whole machine, with a
crank at each end for the compressor, and on this shaft is
mounted either the armature of a continuous-current motor
or the rotor of an alternating-current machine. Single-ended
compressors are also constructed by this firm on the same
lines as illustrated in fig. 146, who also build single and
double ended portable compressors, one of the latter being
shown in fig. 147. These compressors have no suction
valve, air being admitted above each piston by means of a
port in the latter, which coincides with a similar port in the
top of each connecting rod; during the suction stroke ; and
near the end of this stroke the piston overruns the ports
cut through the cylinder wall, as shown in figs. 143 and 144,
thus making direct communication between the cylinder and
the inside of the compressor casing, which is arranged to
form a suction chamber. Messrs. Reavell claim that this
feature alone results in a gain of at least 5 per cent in the
volumetric efficiency as compared with compressors having
spring-loaded valves, the cylinders being filled with air at
atmospheric pressure at each stroke, instead of a reduced
pressure due to the resistance of the valve springs. A
special feature about the construction of this quadruple*
compressor is the simplicity of construction and the ease
with which the machine may be dissected for examination or
repair, for on removing the nut which retains the end cap on
the crank pin the whole of the connecting rods and pistons
can be removed without the use of a spanner. The method
by which the connecting rod can be removed is clearly

160 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

161

12AC

162 AIR COMPRESSORS AND BLOWING ENGINES.

****-*is**»f-~' — *^'"' ^i/

AIR COMPRESSORS.

163

164

AIR COMPRESSORS AND BLOWING ENGINES.

shown in figs. 148, 149, and 150. The delivery valves are
fitted at the outer end of each cylinder, and they open

Fio. 151.

daring the compression stroke as soon as the air has reached
the required delivery pressure, and through them the air
passes to the delivery belt or passage shown, from which it

AIR COMPRESSORS.

165

may pass away through any of the four openings provided.
These valves are made from steel, and are very light. By
using a number of valves to each cylinder their weight and
lift are reduced to the minimum, thus ensuring freedom

from undue wear and silence in working. This valve, with
seat, cap, and spring, is shown in fig. 151. The annular part
of the casing, figs. 143 and 144, forms a water jacket.

[, — ..--J—

AIR COMPRESSORS. 167

Messrs. Reavell also construct a type of compressor having
vertical compound steam cylinders and horizontal com-
pressing cylinders. One of these is shown in figs. 152 and
153.

41. Air Compressor Delivery Valve constructed by the
Guteho/nungshutte, Oberhausen a. d. Ruhr. — Figs. 154
and 155 show one of four delivery valves for the two air-
compressing cylinders of a twin air compressor. The former
is a sectional elevation, the latter a plan, the upper part of
which shows the valve guard, numbered 2, as seen from
below the lower part showing the valve soat 3, seen also
from below. The parts are all numbered, 1 being the valve-
box cover of cast iron, 2 the valve guard or stop of the same
metal, 3 the valve seat of cast steel, while 4 and 5 are two
rings of steel plate forming the valve. There are eight
spiral springs, numbered 6 and 7, the former exercising a
force of 12 Ib. when they are compressed about J in., and the
latter 21 Ib. for the same compression. These springs are
coiled round 8 and 9, studs upon which grooves are cut for
the ends of the spiral springs. The valve guard is fitted
upon a central bolt 10, and a stuffing box is fitted in the
centre of the cover. The inside diameters of the two rings
are 240 and 120 mm. or 9*45 and 4*72 in. The rings are
30 mm. or 1*18 in. in width. Figs. 156 and 157 are indicator
diagrams from air-compressing cylinders made by this firm,
while 158 and 159 are tnose from the steam cylinders.
The mean pressure p is given in atmospheres. The
horse power of the air cylinders is 923, and that of the steam
cylinders is 1,157, so that the mechanical efficiency is about
80 per cent. The volumetric efficiency is 87 per cent, and
the pressure to which the air is compressed is 6 '6 atmospheres,
and the average mean pressure per square inch of the four
diagrams is 33'31b., the ideal mean pressure

p. = -87 x 2h hyp log ^i

the volumetric efficiency being '87 ;

pt = -87 x 14-7 x 2-3 log 6'6 = 24 Ib.

168 AIR COMPRESSORS AND BLOWING ENGINES.

tOJ

AIR COMPRESSORS.

169

FIG. 157.

1 *267

FIG. 158

170 AIR COMPRESSORS AND BLOWING ENGINES.

Hence the air efficiency

*/2 = ^73 = 1 2 per cent,

and the total efficiency of the engine is

7y = -80 x -72 = -576, or 57 '6 per cent.

77-73

7^-326

3/5

FIG 159.

Taking the diagram in which the indicated horse power is
241, and using the equation,

n = - ..-

log vz - log -P!

log 6-56 - log 1 _
log 98 - log '23'75

42. Professor Guttermuth's Spring Clack Valves. — These
are constructed by the Humboldt Engine Works, Kalk, near
Cologne, and are shown in figs. 160, 161, and 162. The
valve itself consists of a thin plate, which for 50 atmo-
spheres need not exceed 1 mm. in thickness. It is coiled at
one end into a spiral form, and fits at this end into a groove
in a spindle, which is fixed whilst the valve is working, but
which can be rotated so as to tighten or loosen the spring for
high or low speed's of rotation. The three principal faults
of valves in general are the great resistance to the passage
of fluid through them ; the harmful effect of their masses,
producing shock and noise, and destroying the valve seats ;
the great changes of direction and velocity, and the eddies
consequent upon this produced by the valve. To get rid of
these Professor Guttermuth carefully studied the working of

AIR COMPRESSORS.

171

valves, both practically and theoretically, and claims to have
designed one in which all these faults are reduced to the
minimum possible. The mass of the valve is very small, as
is also the tension of the spring, while the flow through the

FIG. 160.

seat and past the valve is so arranged that there is very
little change of velocity and direction, and consequently
very little loss by the production of eddies. This is very
clearly shown in fig. 161, which contains a transverse and
longitudinal section of an air-compressor cylinder. In the

FIG. 161.

latter the air enters from the left, and it will be seen how
small is the change of direction in its passage through the
valve, while the same holds good for the discharge. The
opening of the valve is not affected appreciably by the

172

AIR COMPEESSOKS AND BLOWING ENGINES.

tension of the spring, but depends upon the volume flowing
through it. The spring is necessary merely to close the
valve with sufficient rapidity. The valves are noiseless in
their action, and easily accessible. Fig. 162 shows their
arrangement for an ammonia compressor where a small

FIG. 162.

clearance is necessary. Two small covers are arranged to
give access to the valves. Fig. 163 gives the diagrams of a
compound air compressor made at the Humboldt works,
compressing to seven atmospheres. The diameters of the
steam cylinders are 630 and 950 mm. (24'8in. and 37'4in.),
and those of the air-compressing cylinders 400 and 650 mm.

AIR COMPRESSORS. 173

(15*75 in. and 25*6 in.), while the stroke is 1,000 mm.
(39 -4 in.).

The speed at which the diagrams are taken is 75
revolutions per minute, but the engine is capable of
discharging 5,000 cubic metres of free air per hour. The
ease with which the valves work is shown by the fact that
the pressure on the diagram only exceeds seven atmospheres
by about 3J lb. at most. The advantage of compounding is
also shown by the great reduction in volume of the air in
the intermediate reservoir. The mean volume of air dis-
charged from the low-pressure cylinder is 0*436 of its
volume, while that drawn into the high-pressure cylinder is

FIG. 163.

*95 of its volume. 1^ follows that the air discharged from
the low-pressure cylinder h'as a volume whose ratio to that
of the air drawn into the high-pressure cylinder is

•436 x (650)2 =

•95 x (400)2

The pressure at discharge from the low-pressure cylinder is
27*45 lb., and from the high-pressure cylinder 88'21b,, both
above the atmosphere. The average volumetric efficiency of
the low-pressure cylinders is 94 per cent ; that of the high-
pressure cylinders is 94J per cent. The mean pressures
from the low and high pressure cylinders are 16*12 and
30*65, so that the mean pressure referred to the low-pressure
cylinder is 29*57 lb. per square inch.

174 AIR COMPRESSORS AND BLOWING ENGINES.

The ideal mean pressure that would be obtained with
isothermal compression and volumetric efficiency of '94 is

•94 x 147 hyp log 7 = 26'85.
The air efficiency

~'h = ^^ = 91 P^ cent,

a very good result, showing the advantage of compounding.

If we assume that the mechanical efficiency of the engine
is 80 per cent (and it is hardly likely to be less), we get a
total efficiency of 72*8 per cent ; while with an average
mechanical efficiency of 85 per cent it is 77*2.

The value of the exponent n in the low-pressure cylinder
is calculated from the formula —

log A - logjJ2

log vz - log t\

where <»2 is the length on the diagram between the feet of
the compression and expansion curves, and ^ is the length
measured parallel to the atmospheric line between these
curves from the highest point on the expansion curve ; while
pl must then be chosen as the pressure corresponding to this
point, and p., is the pressure at the foot of the compression
curve —

_ log ^2_-. logU-7 =
log 90-5 - log 41 -25

mean values of plt p»9 vlt v.2 being taken from the two
diagrams.

In the high-pressure diagram we get

log 85-2 - log 39 _ ,

to'O - log 45

The following dimensions of this engine will be of
interest : —

Piston-rod diameter .............................. 125 mm.

Tail-rod diameter ................................ 115mm.

Crosshead gudgeon diameter .................. 130mm.

Bearing length ............. . ...................... 250 mm.

AIK COMPRESSORS. 175

Length of connecting rod 2,500 mm.

Diameter at small end 120 mm.

Diameter at large end 150mm.

Overhang of crank 630mm.

Diameter of journals 325mm.

Length of journals 540mm.

Diameter of shaft at flywheel 430 mm.

Length of flywheel boss 600 mm.

Diameter of crank pin., 190mm.

Length of crank pin 270 mm.

Diameter of flywheel 5,000 mm.

Width of rim 300mm.

Radial depth 300mm.

Number of arms 8

Centres of cylinders 4,450 mm.

Diameters of side shaft 80 and 90 mm.

Diameter of mitre bevel wheels 640 mm.

Diameter of high-pressure steam and exhaust

double-beat valve '. . . .> 180 mm.

Diameter of low-pressure steam' and exhaust

double-beat valve 1 290 mm.

Diameter of high-pressure steam pipe 175 mm.

Diameter of high-pressure exhaust pipe 200 mm.

Diameter of intermediate receiver /835mm.

Length of intermediate receiver 2,540 mm.

Diameter of low-pressure steam pipe 275 mm.

Diameter of low-pressure exhaust pipe 325 mm.

Diameter of low-pressure air cylinder suction

pipe 300mm.

Diameter of low-pressure air cylinder dis-
charge pipe 275mm.

Two intermediate receivers — diameter and

length ...c 575 and 4,200mm.

Diameter of high-pressure air cylinder suction

pipe 225mm.

Diameter cf high-pressure air cylinder dis-
charge pipe 175mm.

Thickness of high-pressure cylinder 30mm.

Thickness of high-pressure liner 35mm.

Thickness of high-pressure air cylinder 25 mm.

176 AIR COMPRESSORS AND BLOWING ENGINES.

Thickness of high-pressure air liner 32 mm.

Total length of low-pressure air valves 1,000 mm. '

Total length of high-pressure air valves 605 mm.

Number of passages in low-pressure gratings 40

Area of each passage about 33 x 42 mm. j

Number of openings in high-pressure gratings 30
Area of each passage 27 x 30mm.

The steam valves are double-beat, and are actuated by
eccentrics from a side shaft. Each cylinder has four valves —
two admission above and two exhaust beneath. A trip gear
is used, the cut-off in the low-pressure being adjustable t»y
hand, and that in the high-pressure being controlled by the
governor.

43. The Boreas Air Compressor, constructed by Messrs.
Alley and MacLellan.* — This is a two-stage compressor.
The air enters the upper end of the cylinder through valves
in the cover, fig. 164, on the down stroke, and is discharged
on the up stroke through valves at the side, fig. 165, into a
long pipe, which forms a receiver and intercooler between
the upper and lower side of the piston. As shown in fig.
165, this pipe is immersed in a tank in the base of the
machine, which forms a reservoir for the water circulated
through the cylinder jacket. The lower side of the piston
has a trunk, so that the air is again compressed on the down
stroke, the suction and discharge valves being shown in
fig. 165 at the side of the cylinder. These, as also the
discharge valves for the upper side of the piston, are con-
tained in boxes quite distinct from the cylinder proper, and
are readily accessible for inspection and renewal. The crank
is lubricated on the splash system, and is completely
enclosed. Other working surfaces are kept oiled by a
system of forced lubrication worked by the small pump
without valves, which is at the right end of the crank shaft.
This draws oil from a well in the casing through a filter, and
delivers it to the different bearings. The oil is returned
again to the well from oil catchers In order to regulate
the machine there is a pneumatic switch, adjusted for any
desired pressure, which, when this pressure is reached on

* Engineering, October 4th, 1903.

AIR COMPRESSORS.

177

13AC

178

AIR COMPRESSORS AND BLOWING ENGINES.

the receiver, turns the air discharged from below the piston
back to its upper side, so that the air simply circulates
through the machine, no work being done except that
necessary to overcome frictional resistances. The pressure
is thus very closely regulated.

44. The Brotherhood Air Compressor. — Fig. 166 is a
front elevation of a small compressor constructed by this

FIG. 166.

firm for a pressure of 125 atmospheres. A is the com-
pressing cylinder, and B are two steam cylinders. The rod
of the air cylinder is attached to the centre of a crosshea<l,
to whose ends the steam piston rods are connected. The
crosshead is guided vertically by four guides G, which also
form the engine columns. The connecting rod drives the
crank shaft, upon which are two flywheels, and the valves
are driven from pins on these. Fig. 167 is a sectional
elevation through the air cylinder, by which it will be seen
that the compression is performed in three stages. When
the piston D descends, air is drawn in above it through the

AIR COMPRESSORS.

179

valve in the cover. On the up stroke this air passes through
valves in the piston into the annular space A, so that, its
volume being reduced, its pressure rises ; on the down
stroke it is compressed in this annular space, and passes

Pio. 167.

down passages M into the annular space above the piston E,
so that its pressure is still further increased. On the ii[>
stroke the air is still further compressed and passes the
valve K, and flows in a spiral tube L, which is enclosed in

180 AIR COMPRESSORS AND BLOWING ENGINES.

a tank of water and connected to the air reservoir. The
cooling water is not only sprayed into the cylinder with the
inflowing air, but also circulates within the piston in the

FIG. 1C8.

space C and the tank S. The manner in which the circu-
lation is carried out is partly shown in fig. 168, which is a
sectional elevation on a plane perpendicular to the axis of
the shaft. The water enters the pipe N, and is drawn into
the annular space surrounding the pipe Q, the water flowing

AIR COMPRESSORS.

181

in as the piston D descends, and passing the valve P into
the space C. On the up stroke the water ascends Q, passes

FIG. 169.

the valve at the top, and flows by R into the tank S
surrounding the air cylinder, which it leaves by the passage

182

AIR COMPRESSORS AND BLOWING ENGINES.

T. This type is capable of compressing 10 cubic feet of air
p^r hour at a pressure of 100 atmospheres, and weighs only
5 cwt. A larger one, fig. 169, with two compressing
cylinders, has a capncity of 20 cubic feet of compressed air

Fto. 170.

per hour, and both can, if necessary, work up to a pressure
of 2,500 Ib. per square inch. Three-cylinder engines are
also constructed.

45. Sentinel Air Compressors, constructed by Messrs.
Alley and MacLellan of Glasgow. — Through the courtesy
of Messrs. Alley and MacLellan we are able to describe
their latest improvements in this type of compressor. Fig.

AIR COMFHESSOBS.

183

170 shows an outside view, and fig. 171 a sectional
elevation of their series B two-stage vertical type, fitted
with intercoolers and forced lubrication. In fig. 170 the
suction port is visible in the centre of the top, and the
discharge to the left. It will be seen from fig. 171 that
the piston valve has three pistons ; on the down stroke
of the main piston the piston valve is above mid-stroke and
is admitting air to the top of the main piston from the space
between the top and middle piston valves which is in

LR DISCHARGE.

GATHERING CYLINDER

FIG. 171.

Connection with the suction port. In the annular space
below the main piston the air is being compressed, and
when the valve has risen sufficiently it flows to the H.P.
discharge valves, lifting these when compressed to the
reservoir pressure. The piston valve closes the discharge
port just at the end of the stroke, and descending further,

184

AIR COMPRESSORS AND BLOWING ENGINES.

forces the air beneath it through the discharge valves ; at
the same time these latter are seated very quietly because
they have beneath them a cushion of high-pressure air. On
the up-stroke air is forced from the large space above the
main piston into the annular space below it, to reach which
it has to pass through the intercooler b eneath the engine,
which consists of pipes immersed in a reservoir of water,
from which that used in the cylinder water jacket is drawn.
Lubrication is effected by means of the force pump at the

FIG. 172.

right end of the crank shaft. This type is constructed in
five sizes, delivering from 100 to 600 cubic feet of free air
per minute. Messrs. Alley and MacLellan also make this
class of compressor with two or three cylinders deliver-
ing a proportionate quantity of air. The valves in fig. 171
are thin rings of steel, but the types shown in fig. 172 are
an improvement on these. They are of steel, drop-forged,
and are kept on their seats by springs. Fig. 173 shows the
piston and discharge valves, and also the arrangement of
the automatic air-inlet control valves. On the left of the
piston valve will be seen the balanced thottle valve, through
which the air from the suction port must pass to reach
the piston valve. The throttle valve is raised or depressed
by means of a spindle, upon the top of which is a piston,
called the control piston, forced down by a spring, so th»t
unless a sufficient air pressure acts underneath it the throttle
valve will remain open. As long as the pressure in the
reservoir or discharge pipes does not exceed that required
by 2 lb., there is only atmospheric pressure under the control
piston, for the pipe connecting it to the air governor on its
left is connected to the atmosphere by means of the

ATR COMPRESSORS.

185

adjustable leak screw. But when the pressure rises above
this the air governor admits air underneath the control

H.P. Suction from
Interaoaler

FIG. 17?.

piston and raises it, thus closing the throttle valve, so that
the only work required to drive the machine is that needed

186

AIll COMPRESSORS AND BLOWING ENGINES.

to overcome friction. The air governor is shown to a larger
scale in fig. 174; it consists of a flexible copper diaphragm
heM between the two parts of the casing and loaded on the
top by an adjustable spring ; the function of the bolt in the
centre is to reinforce the diaphragm and to receive and

ToReceirer

FIG. 174.

transmit the load of the spring to the small valve at the
bottom with a conical head ; the connection with the
receiver is on the left in fig. 173, and on the right in fig.
174, just above the valve. When the pressure rises 2 Ib.
above the normal the diaphragm is raised, and the valve is

AIR COMPRESSORS.

187

lifted by the spring beneath ; air then flows underneath
the control piston and closes the throttle valve. In the
steam driven or " Series C " compressors, a further Con-
nection from the air governor controls an equilibrium
throttle valve on the steam inlet, which closes simultaneously

FIG. 175.

with the air throttle. A bye-pass is arranged, which supplies
sufficient steam to keep the machine running light until the
steam and air throttles re-open and the load is resumed.
This ensures the economical running of the compressor
whether light or under load. Fig. 175 is a sectional
elevation of a series D compound double air compressor with
steam cylinders 13 in. and 20 in. diameter, air cylinders

188

AIR COMPRESSORS AND BLOWING ENGINES.

18 in. diameter, with a stroke of 10 in. The piston rods are
2jin. diameter, the crauk-shaft is 5Jin., and the crank pins
are 6J in. long. The cranks are set at 180 deg. The -team
valves are piston valves. The speed governor is on the left

FJG. 176.

end of the shaft, but in addition to this,* in the left-hand
upper corner of the figure, is the air governor for shutting
off steam, except that through the bye-pass sufficient to keep
the engine in motion. When the required pressure is
reached this valve is shut down by the control, and

AIR COMPRESSORS.

189

immediately after the air suction is shut off. On the
pressure again falling the steam equilibrium valve opens
first, 'running the machine up to speed, and then the air

FIG. 177.

control opens, taking up the compression again. Fig. 176
shows a series J air compressor. These are made of the
following capacities in cubic feet per minute : 500, 1,200,
1,500, 2,000, 2,500, 4,000, and 5,000.

190

AIR COMPRESSORS AND BLOWING ENGINES.

Where only a small amount of compressed air is required,
or where it is not constantly used, or for low-pressure work,
Messrs. Alley and MacLellan recommend their "Sentinel

Airlnief Valves '

FIG. 178.

Junior " single-stage air compressor. One of these is shown
in fig. 177. The machine is completely enclosed, and the
pistons are single-acting. The valves, which are similar to
those shown in fig. 172, are placed in the cylinder cover and

AIR COMPRESSORS. 191

are self-acting. There are only six bearings in the machine ;
these are of ample proportions, and working as they dor
protected from flying grit and dirt and in an oil bath, run
for very long periods without attention. The valves work
successfully at 1,200 revolutions per minute. This type of

Fin. 179.

compressor can be fitted with a governor which is a modifica-
tion of that already described, the control piston being shown
in fig. 178. When this is depressed by air pressure it forces
open two air inlet valves by means of the two f in. spindles
fastened to it. Thus the compressor continues to run
without doing any work. Want of space prevents the
description of several other types of compressor constructed
by this firm.

Fig. 179 is a diagram from a two-stage compressor of
series B, taken at 225 revolutions per minute. The receiver
pressure is 100 Ib. per square inch and the scale is TJ^.

46. High-pressure Air Compressor, by MM. Elwell
Fils, Plaine St. Denis, Paris.* — Fig. 180 is a sectional
elevation through both cylinders. Figs. 181 and 182 are
also sectional elevations through the small and large
cylinders, both at right angles to the shaft, and fig. 183 is a
sectional elevation through the large cylinder. The com-
pressor is intended for a pressure of 1,430 Ib. per square
inch, and the air is compressed in four stages. On the
down stroke of the large piston the air is drawn into the
cylinder through the eight valves E, E, fig. 183, in the
cover, which are closed by helical springs. A spray of water

* From the Engineer, March 16th, 1894.

192

AIR COMPRESSORS AND BLOWING ENGINES.

is introduced at the same time, and a small quantity of oil
is drawn in from the lubricator. When the piston ascends

FIG. ISO.

FIG. 181.

it compresses the air above the piston until it is able to open
the valves F in the piston and to enter the annular space B,

AIR COMPRESSORS.

193

FIG. 182.

UAC

194 AIR COMPRESSORS AND BLOWING ENGINES.

so that compression goes on with diminishing volume until
the end of the stroke, when the pressure is about 571b. On
the return stroke the pressure is raised to 142 lb., and the
air is forced into a coil of pipes connecting the large with
the small cylinder, and as this is in a tank filled with water
which is kept in motion by a pump, the air is cooled before
it enters the small cylinder by the central valve at the top.
The air passes through the valve in the small piston on its
up stroke into the annular space beneath, and its pressure
is then raised to 430 lb., and on the return stroke it is dis-
charged at 1,430 lb. It is to be noticed that the water
introduced into the first cylinder passes through all the
stages, and is always above the valves. It is claimed by the
makers that this is a feature of considerable importance in
high-speed machines, because there is no danger of knocking
a cylinder end out, or breaking the piston if too much
water should be admitted. These compressors are specially
designed for charging torpedoes, and are used in the French
Navy. The leading dimensions of the machine shown are : —

Diameter of large air piston — 210 mm. (8 '2 6 in.)

Diameter of trunk 180 mm. (7*1 in.)

Diameter of small piston 66 mm. (2*6 in.)

Diameter of trunk 55 mm. (2 '17 in.)

Diameter of steam pistons 180 mm. (7*1 in.)

Stroke of all pistons 150mm. (5*9 in.)

A general view is shown in fig. 184, in which it will be
seen that the air cylinders are at the top and the steam at
the bottom. The steam piston rods are connected to the
air trunks by means of two rods and two crossheads, and
the crank shaft is driven by two connecting rods fastened
to gudgeons in the air trunks. The valves are driven by
eccentrics on this shaft, and the circulating plunger pump,
which is to the left of fig. 184, is also driven by it by means
of two connecting rods and a lever. Another size, intended
to discharge 17*65 cubic feet of air at l,4001b. pressure, has
the following leading dimensions : —

Fio. 184.

106 AIR COMPRESSORS AND BLOWING ENGINES.

Diameter of large air piston ^sin-
Diameter of trunk 6f in.

Diameter of small piston 2-| in.

Diameter of trunk. 1 T\ in.

Diameter of steam pistons 6J in.

Stroke of all pistons 4 J in.

Revolutions per minute 300 to 350

Steam pressure — 43 Ib. to 71 Ib. per square inch.

47. Air Compressor Cylinder, constructed l>y the
Allis-Chalmers Co., Milwaukee. — The inlet valves are of
the Corliss type, and the discharge are self-acting. The
wheel at the side is driven by an eccentric rod, whose end is
attached to the pin, which in fig. 185 is at the lowest point

FIG. 185.

of the wheel. The connecting link and valve levers are so
set that their motion is very small when the valve is closed,
i.e., when pressure acts upon it, so that waste of power by
friction is minimised. The valve is balanced when closed, a
small passage above the suction connecting the cylinder to
a space at the back of the valve. The discharge valve has a

AIK COMPRESSORS.

197

spherical seat, and is guided by a projection on the cover,
which also forms a dashpot, cushioning the opening of the
valve. There is also a central spring fitted in a cylindrical
case with the right end closed, which presses the valve on
its seat.

CHAPTER VI.

48. Double Kin<j Riedler Air Compresso?-.* — This was
constructed by Messrs. Fraser and Chalmers, of Erith, in Sep-
tember, 1901, for the Powell Duffryn Steam Coal Company.

FIG. 186.

Its capacity is 8,300 cubic feet of free air compressed in two
stages to 60 Ib. pressure at 70 revolutions, with a boiler

* From Engineering, November 14, 1902.

198

AIR COMPRESSORS AND BLOWING ENGINES.

pressure of 95 lb., and an indicated horse power of 1,050.
Figs. 186 and 187 show that it consists of two compressors
side by side, with a flywheel between, whose diameter is
16 ft., and which weighs about 16 tons. Each half can, if it
is desired, run independently of the other by uncoupling the
connecting rods. The steam cylinders are 23 in. and 38 in.,
and the air cylinders 23 in. and 37 in., the common stroke
being 48 in. All the air pipes to and from the cooler are
fitted with Hopkinson's gate valves, so that either side may

Fio. 1S7.

be rapidly disconnected and one side run alone. The cranks
are set opposite so that the engine is balanced, and the tri-
angular connecting rod not only reduces the height of the
engine, but also gives as uniform a turning moment for each
half as would be obtained with two cranks at right angles.
Fig. 187 shows the connecting rod very clearly. Shoes on
the lower ends of the two piston rods slide in single guides A,
and are coupled by short links B to the bottom angles of the
triangular frame C, of which the apex is on the crank of the

AIR COMPRESSORS.

FIG. 1SS.

Fio. 189.

Fio. 100.

200

AIR COMPRESSORS AND BLOWING ENGINES.

flywheel shaft. A pivoted radius link D is connected in the
middle of the base of the frame so that the linkage practically

FIG. 191.

connects the piston rods to the crank shaft as if they acted
on two cranks at right angles. Figs. 188, 18?, and 190

AIR COMPRESSORS.

201

show the high pressure air cylinder, and fig. 191 a sectional
elevation of the low. They are connected to the steam
cylinders by cast-iron distance pieces, which are in halves, so
that they may be removed after the weight of the air cylinder

FIG. 192.

FIG. 193.

has been supported by bottle jacks supplied with the engine.
The lower covers can then be removed and the pistons
examined. The valves are Riedler's patent, and are
mechanically controlled. There is one suction and one
delivery valve in each cylinder head, arranged as in fig. 190.
The valves for the high pressure cylinder are shown in figs.
192, 193, 194, and 195, the two former giving the suction

FIG. 194.

FIG. 195.

valve and the two latter the delivery. The inner diameter
of the outer seat of both is 10 J in., and the outer diameter of
the inner seat is 5f in. The same dimensions for the low-
pressure valves are 15 Jin. and 9|in. The latter are very

202

AIR COMPRESSORS AND BLOWING ENGINES.

similar in construction to the former. The lift of the high-
pressure valves is 1 Jin. and of the low-pressure li in. No
springs are used, so that ^extremely little force is required to
open the valves, and they are closed as shown in .figs. 196

FIG. 196.

Fio. 197.

and 197 ; the former showing the tappet acting upon the
upper flange of the suction valve, and the latter the same for
the delivery. These tappets are oscillated by means of the
Corliss gear, fig. 202. The tappets do not control the motion

Cr Bore

Fio. 198.

Fio. 199.

while the valve is opening, but shortly before it should close,
the tappet brings it very close to its seat, so that when it
closes by pressure it does so without shock. Dashpots are
fitted at the top of cash valve, so that they open without
shock. In the delivery valves the air discharged at the

AIR COMPRESSORS.

203

inner seat escapes through the passage formed in the guide.
In all these valves care is taken to ensure efficient lubrica-
tion. Oil pipes are connected up to the seats, and through
these oil is forced under pressure from a special oil pump
driven from the engine shaft. The air pistons are of cast
iron, fitted with spiral springs, and the air cylinders are
water jacketed by means of a liner forced into the barrel and
secured in position by copper rings caulked in place, figs.
198, 199, 200, and 201. The outer jacket is provided with
a number of hand holes for scraping and cleaning out the
water jacket space. The cooler, which is common to both
sides, is placed under the floor, and consists of a boiler-plate
shell having |- in. brass tubes, through which water circulates.
Cast-iron pipes connect the air cylinder to the cooler. Each
engine is controlled by a Whitmore combined air and speed
governor, fig. 204. The two governors are connected

FIG. 200.

FIG. 201.

together when both engines are running. They are designed
to control the engine according to the amount of air required,
and to keep the engine running at its minimum speed when
no air is needed. Again, should more air be required than
the engine can deliver, the governor will prevent it from
exceeding its greatest speed. As shown in fig. 202, the
governor bar is connected at one end to a ball governor, fig.
204, and at the other end to an air pressure governor, fig.
203. Increase of speed or air pressure raises the free end of
the governor bar. This motion alters the position of the

FIG. 202.

AIR COMPRESSORS.

205

trip cams of the Corliss gear, and makes the cut-off earlier.
The air governor, fig. 203, consists of a casing G, the interior
of which is connected through an open pipe with the air
receiver. A piston M is connected at the top by suitable
link work with the governor bar, and at the bottom with a
spring D and also by a link H with the plunger E, which

FIG. 203.

FIG. 204.

fits comparatively loosely in its cylinder. As the pressure
rises in excess of that required, for which the spring is
adjusted, the piston M rises and cuts off steam in the
manner already explained. If the pressure were suddenly
reduced, e.g., by the bursting of a main, the compressed air
which has collected below the plunger E will force it up, and
by means of the linkwork I H K, raise M, cutting off steam

206 AIR COMPRESSORS AND BLOWING ENGINES.

exactly as before. The steam valve gear is Reynolds' Corliss
gear, with separate eccentrics for the exhaust and steam
valves ; fig. 202 shows the manner in which motion is taken
from these. We have already stated that the I.H.P.
developed was 1,050 at 70 revolutions to the minute, their a
being compressed to 60 Ib. pressure or 74*7 absolute. The
statement that 8,300 cubic feet of free air is compressed per
minute implies that the volumetric efficiency is unity.
Assuming this, the ideal horse power required to compress
to 74 '7 or 5'1 atmospheres isothermally is

^, hyp, log?-.

33,000

14-7 x 2 x 37'2 x 7854 x 8 x 70 hyp. log-. 5'1.
33000.

= 870.
The total efficiency

Even if we assume a volumetric efficiency of 90 per cent,
which is rather lower than we should expect with such
valves and the probable smallness of the clearance, this only
reduces to

>/! = -9 x 83 = 74*7,

a very good result. With a volumetric efficiency of 95 per
cent, this becomes nearly 79 per cent.

49. Compound Air Compressor with Mechanically-
controlled Valves.* — This engine is constructed by the
Philadelphia Engineering Works, of Merlin Street, Phila^
delphia. It consists of two air cylinders of 23 in. and 38 in.
diameter, whose pistons are driven direct by those of two
steam cylinders 22 in. and 40 in. in diameter; the stroke is
48 in., and the boiler pressure 125 Ib. The engines are
horizontal, and they are arranged as usual, tandem fashion,
the two high-pressure cylinders being in line, and also the
two low-pressure. The crank shaft carries a flywheel 20 ft.
in diameter, weighing 54,000 Ib., and the cranks are at right

* Engineering, October 3rd and 31st, 1901.

AIR COMPRESSORS.

207

angles. The valves, both steam aud air, are actuated by-
Corliss gear, but we intend to confine our description to the

air cylinders. The high-pressure cylinder casting is shown
in figs. 205 and 206, from which it will be seen that there is

208 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

a water jacket ; the low-pressure is similar in design. The
cover, figs. 207, 208, and 209, shows the valve casings and

FIG. 210.

arrangement of passages, while fig. 210 is a sectional eleva-
tion of the cylinder and valves, the lower being the suction

Fio. 211.

and the upper the discharge valve. These are operated by a
wrist plate, connecting rods, and levers, fig. 211 ; but while

210

AIR COMPRESSORS AND BLOWING ENGINES.

the motion of the suction valves is entirely dependent upon
that of the wrist plate, the motion of the discharge valves is
dependent upon the air pressure in the cylinder. The
valves are shown in figs. 212 and 213, the first showing the
discharge and the latter the suction valves. Figs. 214 and
215 show the manner in which the discharge valve is

f?r^

FIG. 212.

opened. In fig. 214 there is a trunk piston, connected by a
link to a lever, which moves the valve. The lever is not,
however, directly connected to the valve, whose stem can
rotate in its boss through a small angle ; the trunk piston is
connected at the large end to the cylinder, and on the
annular surface to the pressure pipes, so that the valve is
opened slightly before the pressure in the cylinder reaches

that in the pipes. The opening of the valve is shown in fig.
215, the part of the valve over the passage being dotted.
Near the end of the stroke the wrist plate forces the valve
back again to the closed position, and the valve remains
thus because the pressure on the annular side of the trunk
piston is greater than that on the side connected to the

ATR COMPRESSORS.

211

cylinder, in which the pressure falls to that of the suction.
Figs. 216, 217, and 218 show the air cylinder diagrams, the
combined steam diagram, and the combined air diagrams.
From these it appears that the air was compressed to

FIG. 214.

RPM 63*

38 • Compressor CylJIP M 63k
Head, end,

FIG. 216.

FIG. 215.

lll*71b. absolute, while the steam pressure was 1281b. by
gauge. The mean load on the two air pistons was 39,643 lb.,
while that on the steam pistons was 43,316'51b., showing a
mechanical efficiency of 91-5 per cent. The mean pressures

212

AIR COMPRESSORS AND BLOWING ENGINES.

in the high and low pressure air cylinders were 43*2 Ib. and
19'4261b. per square inch, which, as the piston areas are
410*25 and 1,128'5, gives a mean effective pressure referred
to the low-pressure piston of 35' 1 Ib. The volumetric

COMBINED OIAC«»W Of
tCUUH Ar'COMUNSCK If tft TO COMOCHStH LOMC AND CfDOUtt I

FIG. 217.

I NO Pl$TOH HOD ARfJk '

is or ™*r ncctivco

FIG. 218.

efficiency of the low-pressure cylinder appears from fig. 216
to be unity; consequently the ideal mean pressure is

pt hyp. log. £ - 14-7 x 2-3 log. !^ = 297,

so that the air efficiency

297
= -^y = 84-6 per cent,

AIK COMPKESSOBS.

213

214

AIR COMPRESSORS AND BLOWING ENGINES.

and the total efficiency of the engine is

91-5 x -846 = 774 per cent.

The revolutions are 63^ per minute, so that the piston speed
is 508 ft. per minute.

50. Air Compressor by M. Joseph Francois, Serainy.*
Figs. 219 and 220 show a sectional elevation and end view
partly in section of an air compressor for working rock drills.
The delivery valves D, D are conical, and are controlled by
springs ; there are two at each end of the cylinder. The
suction valves, of which there is one at each end, are also

FIG. 220.

conical, with horizontal axis, and are pressed on their seats by
springs. They are opened by levers H, I, connected by a link
K and pivoted on axes E, F, and these levers are made to
oscillate by being connected to the eccentric that drives the
distribution valve. The piston is moving to the right, and
the left suction valve is held open by its lever. The lever
probably opens the valve at the beginning of the stroke, and
holds it open until near the end, when it is almost closed by
the spring, aud of course at the end of the stroke it is
closed entirely. In the paper from which we obtain our

* Engineering, September 3rd, 1897.

AIR COMPRESSORS. 215

information this is unfortunately not made clear, and the
fact that the eccentric must have advance to drive the steam
valves makes it impossible for the levers to open the valve
at the beginning and close it at .the end of the stroke. The
diameter of the steam cylinder is 12 '6 in., that of the air
cylinder is 11*81 in., the stroke being 19 '69, and the highest
speed 80 revolutions and the least 5. At 60 revolutions
and 71 Ib. pressure of air above the atmosphere the horse
power is 25, and the weight of air delivered per minute
6601b. The steam and air cylinders are, of course, in line
and the lever G at one side, so that the left half of fig. 219
is a plan, and the right an elevation.

51. Compound Air Compressor ivith Mechanically-
controlled Valves, constructed by Messrs. Schneider and
Co., Creusot* — The leading dimensions of this engine, of
which four were constructed for the Compagnie Parisienne
de 1'Air Comprime, are : —

Diameter of small steam cylinder 900 mm. (35T7Fin.)

Diameter of intermediate cylinder 1,400 mm. (55Jin.)

Diameter of large steam cylinder 2,000 mm. (78f in.)

Diameter of low-pressure compressors. 1,100 mm. (43Jin.)
Diameter of high-pressure compressors 780 mm. (SOiJin.)

Stroke 1,400mm. (55£ in.)

Diameter of flywheels 5,500mm. (18ft.)

Diameter of air pumps 800mm. (31 Jin.)

Stroke of air pumps 550 mm. (21f in.)

Diameter of intermediate reservoirs... 1,600 mm. (63 in.)
Length of intermediate reservoirs 9,000 mm. (29 \ ft.)

The normal indicated horse power was 2,000 at 60 revolu-
tions; the air pressure, by gauge, 113'81b. per square inch;
and the boiler pressure 170'71b. per square inch.

The engine is shown in figs. 221 to 225. It is vertical,
direct-acting, and there are three cranks ; the air cylinders
are placed above the steam, the high-pressure being in line,
and the two low pressure air cylinders being above the inter-
mediate and low-pressure steam cylinders. The air valves
are mechanically controlled, and those of the steam cylinders

* Engineering, September 23rd, 1898.

216 AIR COMPRESSORS AND BLOWING ENG1NFS.

FIG. 221.

AIR COMPRESSORS.

217

218

AIR COMPRESSORS AND BLOWING ENGINES.

are of the Corliss type. The engine is controlled by varying
the cut-oft' in the high-pressure cylinder ; that in the inter-

FIG. 224.

mediate and low-pressure is varied by hand. The governor
prevents the speed exceeding 72 revolutions per minute, and

AIR COMPRESSORS.

219

to prevent the air pressure rising too high, a special governor
slackens the speed when the pressure passes 113'81b. per
square inch (8 kilogrammes per square cm. ). Both governors
act on the same expansion gear. In fig. 222 it will be seen
that there is a bevel wheel at each end of the main shaft
driving two vertical shafts, which, by means of a pair of bevel

Fio. 225.

wheels at their upper ends, drive a horizontal shaft, upon
which are keyed eccentrics whose rods drive the wrist plates
of the steam Corliss gear, fig. 225. The air valves are
operated by cams upon this shaft, figs. 221 and 223, the
valves themselves being of brass with indiarubber flaps, as
shown in figs. 226. 227, and 228, the first, fig. 226, being a
suction valve in half plan and section ; fig. 228 a section
through a delivery valve, and fig. 227 a plan. The
mechanical control in no way affects the opening of the

220

AIR COMPRESSORS AND BLOWING ENGINES.

valve, but near the end of the stroke brings it close to its
seat, so that it closes without shock when a reversal of
pressure takes place. The condensers, air, feed, and drain
pumps are below the engine room floor level, in a space
12 ft. deep, well lighted, and free of access. There are two
single-acting air pumps, each a little more than one-sixteenth
of the volume of the low-pressure cylinder, worked by cast-
iron levers driven by the small and intermediate piston rods.

FIG. 226.

Air is drawn in through the louvres on the roof, which are in
communication, through the box girders and hollow pillars
that support them, with the two low-pressure compressing
cylinders. Special pumps with valves worked mechanically
on the Riedler system, and independent of the main engines,
deliver the water necessary for cooling the air in the com-
pressors and intermediate reservoirs.

AIR COMPRESSORS.

221

Several efficiency and coal consumption trials were made
with these engines, in one of which the indicated horse
power was 1,996*5 at 59*635 revolutions, with a boiler
pressure of 157*2 lb., a pressure in the high- pressure valve
chest of 146*4 lb., and an air pressure of 102*4 Ib. per square
inch. If the volumetric efficiency of the air cylinders had
been given, this would have enabled us to calculate the total

FIG. 227.

FIG. 228.

efficiency of the engine. The clearances are undoubtedly
small, and with mechanically-controlled valves the admission
line is very little below the atmospheric, so that the volu-
metric efficiency cannot be much below unity. Taking this
value, we have the ideal horse power necessary to compress
to 102*41b. above the atmosphere, or 117*1 absolute is

4- u 144»» va hyp. log. r

Air horse power = - o«mnn —

ooOOO

_ 14-7 x 2 x -7854 x (431)2 x 55 j- x 59*635 x 2 x 2*3 log.7'975

12 x 33000.
= 1485 at 59*635 revolutions.

222

AIR COMPRESSORS AND BLOWING ENGINES.

So that the total efficiency is

* - iS = 74'4 per ceut

The volumetric efficiency is certainly not less than 95 per
cent, which would give a total efficiency of 71 per cent
nearly.

52. Air Compressor, with Equalisation of Pressure at
the End of the Stroke.* — This compressor is constructed by
Messrs. Richardson, Westgarth, and Co., of Middlesbrough,
and is principally of interest as its valves are constructed to
produce equalisation of pressure at the end of the stroke,
and so increase the volumetric efficiency. The slide valve
resembles very closely the distribution valve of Meyer's
expansion gear. It carries on its back another valve, which,
however, moves with it, and is held down by a spring, rising
when the pressure in the cylinder is slightly in excess of

PIG. 230.

that in the valve chest. The air is admitted at the port,
which in a steam engine is usually the exhaust, and is
discharged through the two vertical passages at the end of
the valve. Fig. 231 shows admission taking place on the
right of the piston ; the air is passing through the middle
port, and over and under the small central valve within the

* From Engineering, September 4th, 1903.

AIR COMPRESSORS.

223

larger valve. Discharge is taking place through the left-
hand vertical passage in the slide valve, and the upper valve
is raised. Fig. 229 shows the piston close to the end of its

FIG. 231.

stroke. Discharge has ceased, as the right-hand vertical
passage in the slide valve is now closed, and equalisation of
pressure is just about to commence, while admission on the

FIG. 232.

left of the piston is just at an end. Fig. 230 shows equali-
sation taking place, admission and discharge being both
closed. This construction .provides a large equalisation

224

AIR COMPRESSORS AND BLOWING ENGINES.

passage, which cannot become choked. Fig. 232 shows a,
vertical cylinder and equalisation valve in which two flap
valves are fitted.

53. Messrs. Hughes and Lancaster's Patent Glandless
Corliss Valves. — Fig. 233 is a side elevation of the com-
pressing cylinder, and shows the manner in which the valves
are driven from the eccentric. The end of the eccentric rod
is on the left, and a coupling rod connects the two valve
cranks, of which one, T, is seen on the right. There is only
one valve at each end, V, fig. 235. The piston is moving to
the right, and both valves are turning counter-clockwise ;
the left is admitting air from the suction passage A through

FIG. 233.

the cylinder port G, and the right is connecting the cylinder
to the space D in the valve, but discharge has not yet
commenced, as the non-return valve H, fig. 234, closes the
passage to the discharge F. The piston is, in fact, in such
a position that the air compressed in the clearance has
expanded to atmospheric pressure, and as the delivery lap is
equal to the admission lap, the valves open simultaneously.
The valve diagram has already been discussed in Section 13,
fig. 13, for the motion of the valves V, V is approximately
harmonic. In that figure cn,cr are the admission and delivery
laps ; admission commences when the crank is at c g and ends
when it is on the dead centre c b, the eccentric following the
crank in the direction of the clock, the angle between them
being a c d. On the next stroke the valve opens the delivery
passage D when the crank reaches c t, which is g c produced,

AIE COMPRESSORS.

16AC

226

AIR COMPRESSORS AND BLOWING ENGINES.

so that admission and the opening of the delivery passage
occur simultaneously. The delivery passage is clossd at the
dead centre c a, and the valve H returns to its seat without
shock under the force of the spiral spring, the pressure on
both sides of it being the same. I is a dashpot for the valve ;
H and J are passages allowing the air to escape from it.
The valve lever T is shown in section on the right of
fig. 234. K is the intermediate piece of an Oldham coupling,
and L is the driving fork. As the air pressure produces a

FIG. 236.

thrust to the right, the valve spindle is fitted with a thrust-
piece P, which is lubricated through a small hole in the
centre of the oil piston N, the pressure upon which balances
the end thrust of the valve. M is the balance cylinder,
supplied with oil by the oil reservoir R, to the top of which
air pressure is admitted by the pipe S. The advantages
claimed for these valves are : (1) That the valve is opened and

AIR COMPRESSORS.

227

closed mechanically for suction, which avoids wire drawing
and prevents any leakage past the valve at the end of the
stroke. (2) The delivery valve is shut mechanically, also
preventing leakage, and it is opened automatically. (3) The

FIG. 237.

clearance is small, being not more than 1 per cent of the
cylinder volume in large sizes, so that a high volumetric
efficiency is obtained. The air imprisoned in the Corliss
valve passage D does not affect the volumetric efficiency,
as it is only let back into the cylinder after the compression

228 AIR COMPRESSORS AND BLOWING ENGINES.

stroke has commenced. (4) There is no jar or knock in
valves, and the running is extremely quiet at all speeds.
Very high speeds are obtainable ; e.g., 450 revolutions with
an 8 in. stroke, or 600 ft. of piston speed per minute, which
is very high for such a short stroke. (5) The small number
of valves makes their upkeep small, and there is a smaller
number of moving parts to get out of order. (6) There is
no gland to pack, and the valve is in almost perfect equi-
librium, and the lubrication perfect. The Oldham coupling
allows the valves to follow up their wear with certainty.
(7) Both body and about three-quarters of the end covers
are water jacketed in the spaces W W, and the air at inflow
does not come in contact with any heated surface till it
reaches the inlet valve. (8) Should the valve go wrong,
there is only one cover, which is held down by four studs, to
remove. The engine can be stopped, the valve taken out,
examined, replaced, and the engine re-started on the largest
compressors in less than five minutes. Figs. 236 and 237
are sectional elevations, showing details of construction of
a 22 J in. diameter and 24 in. stroke air cylinder.

54. Air Compressor Constructed by the Worthington
Pump Company. — Fig. 238 is a sectional elevation of the
compressing cylinder, the distinguishing feature of which is
the valve gear, which combines in a very ingenious manner
the positive action, noiseless operation, and durability of the
mechanically moved valve with the elasticity of the poppet
valve ; the noise and rapid wear of the poppet valve, due to
the impact of the valves closing at the end of the stroke, is
eliminated by mechanically closing the passages underneath
the poppet valve, and leaving a cushion of compressed air
upon which the latter seats. The two Corliss valves are
operated by an eccentric on the crank shaft in a manner
very similar to that shown ,in section 50. The action of the
valve gear is clearly shown in figs. 239, 240, 241, which
give the position of the valve at various points of the stroke.
At the beginning of the suction stroke of the piston,
indicated by position 1, fig. 241, the mechanical valve A,
fig. 239, is just about to close port B, the discharge edge of
A being in line with the upper edge of port B, and the
valve moving in the direction shown by arrow C. After

AIR COMPRESSORS.

FIG. 239.

FIG. 240.

230 AIR COMPRESSORS AND BLOWING ENGINES.

the piston advances a short distance, the valve has reached
the position shown in fig. 240, in which the inlet edge of the
valve D is just coming line and line with the lower edge of
port B. The valve continues to move in the direction of
the arrow C until about mid-stroke, when it reverses to that
shown by the arrowr E, bringing the valve back to the
position shown in fig. 240, at the end of the stroke corres-
ponding to position 3 on the ideal card, fig. 241. The
compression stroke now commences, the valve still moving
in the direction of the arrow E. After the mechanical valve
opens, the poppet valves G, fig. 239, which have had the
entire return stroke in which to seat, prevent the How of air
back from the discharge passages to the cylinder, and

Fia. 241.

remain closed until position 5 in fig. 241 is reached, when
the pressure inside the cylinder slightly exceeds that in
the discharge passages. The poppet valves G there-
upon open, and remain open, until position 1, fig. 241,
is reached, at which point the valve A, which in the mean-
time has changed its direction to that shown by arrow C,
has resumed the position shown in fig. 239, thus leaving a
volume of compressed air in the space between the
mechanical and poppet valve, permitting the light springs
back of the poppet valves G to seat them easily and gently
during the return stroke. Thus the three fixed points in
the compression cycle, viz., opening of the inlet, closing of
the inlet, and closing of the discharge, are positively and
mechanically controlled ; the opening of the discharge, the

AIR COMPRESSORS.

231

only variable point in the cycle, is controlled by the auto-
matic poppet valves, which are relieved, however, of the
necessity for quick closing, and are consequently free from

Scarce 30

inch ; 150 revolutions per minute.

232 AIR COMPRESSORS AND BLOWING ENGINES.

the objectionable feature of noise and rapid wear. Two of
these compressors were exhibited working at the St. Louis
Exhibition. Indicator diagrams are shown in fig. 242.

55. Cross-compound Two-stage Compressor constructed
by the Breitfeld Danek Engineering Company for the
Krimich shaft of the St. Pankraz Mine in Nurschau. —
Compressed air has been used for many years in this
mine for driving machinery underground, and when an
increase of power was needed, it was decided to replace
the existing small compressors by a large compound two-
stage machine. This was constructed by the Breitfeld
Danek Engineering Company, of Prague-Karolinenthal, and
since the 9th of March, 1903, has worked without a stop.
At present it drives six hauling engines, ten piston pumps,
three coal cutters, and several ventilators on Korting's
system. The high-pressure steam cylinder has a diameter
of 675 mm. (26'6 in.), the low-pressure 950 mm. (37'4: in.),
that of the small air cylinder is 550 mm. (21*7 in.), and
of the large 875 mm. (34'5 in.) ; the stroke is 900 mm.
(35'5 in.). With a boiler pressure by gauge of 5J atmo-
spheres (81 lb.) and the same air pressure, the engine runs
at 60 revolutions and discharges 60 cubic metres (2,110
cubic feet) of free air per minute, and can, if necessary,
discharge 80 cubic metres (2,820 cubic feet). The high-
pressure cylinder is fitted with Rider expansion gear, and
the low-pressure with Meyer expansion valves. Not only
does the governor control the speed, but also the air
pressure by acting upon the expansion valve. The
centrifugal governor limits the speed to 80 turns. The
air pump is vertical, and is placed beneath the crankshaft
at the right end. It is driven by a connecting link from
the end of the crank, and a lever ; its diameter is 600 mm.
(23'6 in.), and its stroke 250 mm. (9'84 in.). The steam
receiver is provided with a steam jacket, and is also under-
ground, between the cylinders. The compressing pistons
are coupled direct to the steam pistons, and each pair of
cylinders is connected by two rods. Between the air
cylinders, parallel to them and under the floor, is the
intermediate air cooler. The effective length of this is
3,015 mm. (119 in.), and its diameter 800 mm. (31' 5 in).

AIR COMPRESSORS- 233

It contains 156 drawn-brass tubes of 32 mm. (1'26 in.)
outer and 29 mm. (l'14in.) inner diameter, which are
divided into groups by plates in order N to increase their
cooling" action. An inclined plunger pump driven by an
eccentric on the main shaft supplies water to a reservoir,
from which it flows through these tubes. The plunger
diameter and stroke are 175 mm. and 180' mm. (6'9 in. and
7'1 in.). The tubes have an effective length of 3,000 mm.
(118 in.), so that their external cooling surface is 47 square
metres (505 square feet). The intermediate cooler has a
volume of 1'508 cubic metres (53 cubic feet); the tubes
occupy 0'374 cubic metres (13' 15 cubic feet), so that the
cooler contains 1"134 cubic metres (39'85 cubic feet). The
volume of the small air cylinder is 0'21 cubic metre (7'43
cubic feet), and that of the large cylinder 0'54 cubic metre
(19 cubic feet) ; so that the ratio of the three volumes of
cooler, large cylinder, and small cylinder is as 5'40' : 2'57 : 1.
The tubes have a total section of 0'109 square metres (1*17
square feet), while the effective section of the cooler is 0'38
square metre (4'08 square feet), the ratio being 1 : 3'49.
The latter section bears to that of the two compressing
cylinders the ratio 1 : 1'56 : 0'61. Each cubic metre of
air has a cooling surface of 41'44 square metres, or 1 cubic
foot to 12'05 square feet. The air, before being drawn
into the large cylinder, passes through a Moller filter m
the roof, and a manometer shows whether this filter
requires cleaning or not. At each end of a compression
cylinder there is a suction and a delivery valve. In
figs. 243 to 246 are shown mechanically-controlled suction
and delivery valves similar to, although not the same size
as, those used in this engine. Figs. 243 and 245 are
sectional elevation and plan of the delivery valve and
figs. 244 and 246 of the suction. The valves are operated
from the tail end of the expansion valve spindle by levers
outside and inside the valve chest, the latter being fitted
with adjustable springs. These offer no opposition to the
opening of the valves, which is therefore effected by a
difference of pressure sufficient to overcome friction and
inertia, an extremely small quantity, the valves being very
light ; but shortly before the end of the stroke the valves

234 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. 243.

FIG. 244.

AIR COMPRESSORS.

235

are compelled to approach their seats very closely, and
finally close without shock, owing to the difference of
pressure. Thus one valve with a large lift can replace .t
number of small ones. At the normal speed of 60 revolu-
tions the valves work without the least noise, and it is
only at 70 revolutions that their working can be heard,
and then only slightly ; a speed of 85 revolutions is admis-
sible. The valves themselves are of forged steel, and
carry pistons at the ends of their hollow guide spindles,
which work in cylinders so as to limit the strokes of the

FIG. 245.

valves and form air cushions, the force exerted by which
can be adjusted by screws, to the left of the air-cushion
cylinder in figs. 243, and to the left and below it in fig. 244.
These screws, of course, control the rapidity with which
the air can escape from the cylinder. The seat and valve
guides are in one piece, and are of cast iron, while the
air-cushion cylinder is of bronze. The air-cushion screws
can be adjusted for noiseless working from the outside of
the casing. Both suction and delivery valves of the large
cylinder and the delivery valve of the small cylinder have
each two seats 4 mm. broad, but the suction valve of the

236 AIR COMPRESSORS AND BLOWING ENGINES.

FIG. 246.

Total Expansion = 6-6

FIG. 247

AIR COMPRESSORS.

237

latter has only one of the same breadth. In the suction
valve of the small cylinder the air passage is 154'48 square
centimetres (24 square inches), that of the delivery valve
is 151 square centimetres (23'4 square inches). In the
suction valve of the large cylinder it is 397 square centi-
metres (62'5 square inches), and in the delivery valve 393
square centimetres (62 square inches). The effective piston
area of the small piston is 2,312 square centimetres (358
square inches), while that of the large one is 5,950 square
centimetres (922 square inches). The piston areas are
therefore about fifteen times those of the valve passages.
As the mean piston speed at 60 revolutions per minute is
1'8 metres per second, it follows that the mean velocity
of the air through the valves is 27 metres per second
(88'5 ft.). Both compressing cylinders have water jackets,
in which water circulates. The pistons have three cast-
iron rings. The piston rods are of Siemens-Martin steel ;
as also the pins and bolts of the valve gear, which are
hardened. The steam is superheated to 250 deg. Cen.
(482 deg. Fah.). Shoda and Hering superheaters are us;ed.
Combined steam and air diagrams are given in figs. 247
and 248. The following is a list of air compressors con-
structed by the Breitfeld Danek E<nginering Company: —

SINGLE CYLINDER — SINGLE STAGE.

250
9'85
240
9'45
5-6

300
11-82
300
11-82
5—6

400
15-75
380
14-95
5—6

500
19-7
475
19-15
5—6

600
23-65
500
19-7
5—6

700
27-6
575
22-65

5—5

800
31-5
625
24-65
6—8

900
35-5
675
26'6
6-8

Diameter of steam fmm- •
and air cylinders. 1 ing

Steam press, in atmosphere.

Air pressure in atmosphere.

4-5

4—5

Revolutions per minute . . •<

125
to
150

100
to
125

90
to
100

80
to
90

70
to

60
to
70

)c. metres..

2-5—3

5—6

8—10

14—16

19—21

25—28

30-33

34—40

,«....{

88
to
105-5

176
to
211

281
to
352

492
to
572

668
to
739

880
to

984

1055
to
1160

1195
to
1410

AIR COMPRESSORS AND BLOWING ENGINES.

COMPOUND — Two STAGE.

( mm..
Stroke in . . •<

700

800

900

( ins. . .

27-6

31-5

35-5

( mm..
Diameter of H.P. steam cylinder. . •<
( ins. . .

500

575

675

(mm...
Diameter of L.P. steam cylinder . . -(
( ins. . .

735

840

050

f mm. .
Diameter of small air cylinder. . . . •<
(ins. ..

430

500

550

r'mm..
Diameter of large air cylinder 1
(ins. ..

C75

775

875

Steam pressure by gauge in atmosphere. .

6—8

6-8

Air pressure by gauge in atmosphere ....
Revolutions per minute

5-7
70—80

5—7
60 70

5-7
60 70

( c. metres.
Air per minute -J

33-38

43-50

60—70

(c. ft

1160—1335

1510—1760

2110-2460

A test made June 20th, 1903, gave the following
results : —

devolutions per minute, 68.

Mean steam pressure by gauge, 5'6 atmospheres (82'3 lb.).

Mean air pressure by gauge, 5 '8 atmospheresi (85 '2 lb.).

Mean vacuum, 61'4: centimetres (24'2in.).

Injection water, 28 deg. Cen. (82'4 deg. Fah.).

Indicated steam horse power, 437'5.

Indicated compressor horse power, 386'8.

Mechanical efficiency, 88 per cent.

Volumetric efficiency, 97 per cent.

Total efficiency, 71 per cent.

Volume of free air compressed per steam I. H.P. hour,

9'376 cubic metres (330 cubic feet,).
Steam per I. H.P. hour, 7'8 kilogrammes (1715 lb.).
Weight of steam per cubic metre of free air compressed,

0'799 kilogrammes.

AIR COMPRESSORS.

239

Cubic feet of free air compressed per pound of steam,

20 cubic feet,
Temperature of atmosphere, 27 to 29 deg. Cen. (S0'6 to

84'4 deg. Fah.).
Temperature of air entering intermediate cooler, 115 to

136 deg. Cen. (239 to 277 deg. Fah.).

6 /tfm. by Gauge

FIG. 248.

Temperature of air leaving intermediate cooler, 50 to

57 deg. Cen. (122 to 134'5 deg. Fah.).
Temperature of air after compression, 124 to 146 deg.

Cen. (255 to 295 deg. Fah.).

At the St. Pankraz Mine, it may be mentioned, the
compressed air is heated by petroleum burners before its
use in the engines that it drives, and experiments are being
made for the introduction of these burners into the
pressure pipes themselves. It is an unfortunate fact that

240 AIR COMPRESSORS AND BLOWING ENGINES.

the total efficiency of compressors and motors is only about
40 to 50 per cent.

56. Castellain Air Compressor constructed by the Breit-
feld Ddnek Engineering Co., of Prague-Karolinenthal. —
Figs. 249 and 250 show in plan and elevation a belt-driven
Castellian compressor. Fig. 251 is also a section through
cylinders and receiver, showing the Corliss and self-acting
valves. Its working is as follows : Atmospheric air enters
the left-hand side of the large cylinder, being admitted
by the Corliss valve to the left, and slightly below it. This
valve is driven by an eccentric on the shaft, fig. 249, which
also drives the Corliss valve of the high-pressure cylinder.
When the piston moves from right to left the air on the
left side is compressed until its pressure is sufficient to
open the self-acting valve that is placed below the Corliss
valve, and air flows into the receiver. On the other side
of the piston there is at first expansion from the receiver,
and after the discharge from the other side commences
there is expansion from the air on the other side of the
piston and from the receiver, assuming that the rod or
trunk on the right is less than that on the left. If it is the
same size there is no change of pressure, and if greater
there will be compression. In fig. 253, which shows the
indicator diagram on the right side of the piston, the lower
part of the curve shows expansion, and the upper com-
pression, which takes place on the stroke to the left in the
receiver, high-pressure cylinder, and on the right-hand
side of the piston. This is also the suction stroke of the
high-pressure piston, to which air is admitted by the Corliss
valve above its left end. The discharge valve is self-acting,
and is just above the Corliss valve. The Corliss valves
are arranged to close at the end of the stroke, so that the
self-acting valves seat themselves upon an air cushion, and
therefore quietly and without shock. Fig. 252 is the high-
pressure diagram, with mean effective pressure 3' 17 atmo-
spheres; fig. 253 has a mean effective pressure of 0'18
atmospheres, and fig. 254, the low-pressure diagram, 1133
atmospheres. These were taken on the 16th of February,
1904; the speed was 160 revolutions, the two cylinders
200 mm. and 400 mm. diameter (7'89in. and 1578 in.),

AIR COMPRESSORS.

241

17AC

242 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

243

with 300 mm. stroke (ITS in.), and a trunk piston rod of
150 mm. (5'9 in.). If pe is the mean effective pressure
referred to the low-pressure piston in atmospheres,

"OP-"*

20°2

FIG. 251.

The volumetric efficiency on the low-pressure diagram is
0'9821, and the ideal mean effective pressure in atmo-
spheres with isothermal compression,

Pi = hyp. log. 6-8 = 1-912,

the absolute pressure of compression measured from the
end of the high-pressure diagram being 6'8 atmospheres
absolute. The efficiency of compression is, therefore,

1-912 x 0-9821
2-396

= 7 9 '4 per cent.

244

AIR COMPRESSORS AND BLOWING ENGINES.

According to the Breitfeld Danek Engineering Company,
the chief advantages of the system are to be found in the
fact that —

(1) According to the pressure of compression required,
the compressor can be built to work as a two or three
stage machine.

FIG. 252.

3c.m.

*), = i-U3 afs n' *60

75% -Ihg.

FIG. 253.

2 cjrr

Fio. 254.

AIR COMPRESSORS.

245

(2) Compact arrangement of a two-cylinder machine,
saving length as compared to the ordinary tandem engine,
or breadth in comparison with a cross-compound arrange-
ment.

(3) Reduction in the number of moving parts, valves,
etc.

(•i) As twin compressor, each side can be run separately,
so that, according to the amount of air required by varying
demand, either one or both sides of the machine can be
run at will.

(5) Saving in weight and space.

1 Air Inle,
/lirvuriei \ W

FIG. 255.

Fig. 255 shows in outline a portable Castellain com-
pressor with plate valves for use in coal mines. The
smaller the trunk piston rod is made, the greater will be
the variation of pressure in the receiver, the less will be
the work done as the piston moves to the left, and the
more as it moves to the right, so that upon the diameter
of trunk depends the variation of pressure on the crankpin.

57. The " Daw " Compressor.— We are indebted to
Messrs. A. and Z. Daw, of 11, Queen Victoria Street,
London, E.G., for the following description of their
compressors : —

The distinctive features of the air compressors designed
by Messrs. A. and Z. Daw, of London, is the " Daw " method
of directly controlling and balancing the inlet and discharge
valves by the air pressure, by which means the air is
compressed with greater economy, and at speeds of com-
pression hitherto thought unobtainable, with attendant

246 AIR COMPRESSORS AND BLOWING ENGINES.

greater output from the compressor and reduction in first
outlay for plant.

The salient features of the Daw valve gear are its
automatic controlling, adjusting, and balancing action.
The valves are directly controlled and balanced by the
air pressure; have a rapid movement, with quick opening
and closing; and, when once set, the valve gear is self-
adjusting for all speeds and pressures. The valves are
practically noiseless in operation, and the wear and tear
is scarcely appreciable.

" Daw " Inlet Valve. — One large inlet valve (fig. 256)
only is used in each head of the compressing cylinder,
giving a wide opening and free passage. There is no delayed
valve action. During admission each valve is kept wide
open, so that the compressing cylinder is completely filled
with air at the atmospheric pressure throughout the whole
stroke, and during compression there is no loss of any
part of the contained air by reflux to the atmosphere. Like
results are obtained with gas as with air. From this
action of the " Daw " inlet valve full-volume efficiency is
obtained, with corresponding greater economy of power
in compression than is possible with inlet valves which are
operated wholly or partly by " suction pressure," as, owing
to the suction work required to be done to overcome
inertia and spring load, they cannot open, or remain open,
unless the pressure in the compressing cylinder is less than
the exterior pressure. The " Daw " inlet valve system
eliminates the great loss of efficiency due to the throttling
of the air in its admission to the compressing cylinder,
caused by mechanically-operated valves which are closed
gradually, and also by automatic or self-acting valves which
require a small lift, making large numbers of small valves
necessary. The various losses caused by defective inlet
valves are saved by the " Daw " inlet valve system ; and,
although not easily determined, the saving effected thereby
is very appreciable.

" Daw " Discharge Valve. — One large discharge valve
only is used in each head of the compressing cylinder,
and to ensure free delivery it is made the same size as
the inlet valve. As the " Daw " delivery valve is perfectly

AIR COMPRESSORS. 247

balanced and controlled, it offers the great advantage over
all other valve systems that it enables air or other gases
to be compressed without " excess pressure," thus saving
the serious loss of efficiency which this entails. In all
other valve systems the seating always causes " excess
pressure," owing to the valve presenting a greater surface
to the pressure in the receiver than to the pressure
in the compressing cylinder. Further, other valve systems
necessitate the reduction of the seating to the lowest
possible margin, as will be seen from the following calcula-
tions, showing the great loss of efficiency which otherwise
would result. There is some risk also that undue reduction
of the seating may cause the valve to be leaky in actual
work.

A 3 in. circular valve with J- in. seating exposes a surface
of 7'07 square inches to the pressure in the receiver and
4'91 square inches to the pressure in the compressing
cylinder. If, then, air was being compressed to 80 Ib.
gauge, the pressure on the valve on the receiver side would
be 7*07 x 80 = 565'5 Ib., which would have to be balanced
by an equal total pressure — i.e., 565'5 Ib. — on the cylinder
side of the valve before it could open and thecompressed
air be delivered into the receiver. The unbalanced valve,
therefore, necessitates a pressure per square inch of

in the compressing cylinder, or 35'2 Ib. above the required
pressure.

On the other hand, a 6 in. circular valve with 5/16 in.
seating exposes a surface of 28'27 square inches to the
pressure in the receiver, and 22'69 square inches to the
pressure in the cylinder. The total pressure on the receiver
side of the valve before it could open and the compressed
arid would have to be balanced by a pressure per square
inch of

which is an excess pressure of 19'9

* This reasoning neglects the pressure between the valve and its seat, and
therefore over-estimates the lifting pressure.

248 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS. 249

In the latter and most favourable case, owing to the
excess pressure, the whole volume of air in the cylinder
is heated 50 deg. higher than with balanced valves. The
increased work during compression only, which this causes,
according to the law of the equivalence of heat and work,
is 13'4 per cent, and it is much greater for the smaller
valve. Owing to some of the "excess pressure" being
lost during expulsion of the air under the receiver pressure,
the actual loss of efficiency is perhaps not so high as the
13'4: per cent; but, nevertheless, the loss is serious, and
is saved by the balanced-valve system. The "Daw" com-
pressors have a water jacket for cooling the air as
completely as possible during compression.

DESCRIPTION OF ACTION OF " DAW " INLET AND DISCHARGE
VALVES.

Taking first the inlet valve gear, fig. 256 shows the
inlet valve A in an open position. It is pivoted at B, and
opens inwards, its weight and the pressure within the com-
pressing cylinder, and also the strong spring C, tending
to keep it closed.

The valve is opened at the commencement of the suction
stroke through the small slide valve D, which is actuated
by the valve gear E, placing the rear end of small cylinder
F in communication with the receiver through pipe S, so
that the pressure in the latter acts upon the piston G, to
overcome the action of the spring C, and the weight of
valve A, such pressure being maintained and the inlet valve
thereby kept in its open position, after it has been opened,
during the full length of the suction stroke. On the com-
pletion of the suction stroke the small slide valve D is
reversed to exhaust, and the spring C, being thus relieved
from the pressure acting against it, closes the valve. The
small cylinders F and H act as dashpots or buffers, and
ensure the valve opening and closing quietly without shock.
The pressure set up on the inlet valve piston G at the
commencement of the suction stroke is sufficient to ensure
the inlet valve A opening instantly, and the removal of
the pressure causes the equally ready closing of the valve
by the spring C.

250 AIR COMPRESSORS AND BLOWING ENGINES.

The discharge valve is shown in its closed position, the
spring J, pressure in receiver, and weight of valve K
tending to close it. It is pivoted similar to the inlet
valve, and is arranged to open outwards in its relation
to the compressing cylinder, and is enclosed in a casing
in open communication with the receiver, the pressure in
which consequently is always exerted on the back of such
valve.

The discharge valve- K is also balanced through the small
slide valve D, which is actuated by the valve gear, placing
the front end of balancing cylinder L in communication
with the receiver, so that on the pressure in the compress-
ing cylinder becoming equal to the pressure in the receiver,
the latter pressure, acting upon the piston M, balances
the difference in pressures on the discharge valve K, due
to the valve seating, also the spring J, and the weight of
valve, causing the discharge valve to open without
any excess pressure being set up in the compressing
cylinder. As the discharge valve lifts off its seat a portion
of the balancing pressure in cylinder L becomes an active
force, opening the valve rapidly, and maintaining it full
open until the compression stroke is completed. The slide
valve D is then reversed by the valve gear, so that the
pressure in cylinder L is exhausted, and the strong spring
J, being thus relieved from the pressure acting against it,
instantly closes the valve. The cylinders L and N act as
dashpots or buffers, and ensure the valve opening and
closing quietly without shock.

The small slide valve D controlling the small pistons,
governing the opening and closing of the inlet and
discharge valves, are mechanically actuated as follows: —

To the piston rod is connected a short rod R which
actuates the long arm of a lever, the fulcrum T of which
is placed a distance above it approximately equal to the
travel of the piston. Forming part, or connected with
this lever, is a connection nearer to the fulcrum to give a
short travel to the rod Q. This has a sliding connection
U upon the horizontal rod O, upon which are adjustable
stops which actuate the small slide valves D exactly at the
end of each stroke of the air compressor, the valves

AIR COMPRESSORS. 251

remaining stationary at all other times. By this positive
motion it is ensured with absolute certainty that the valves
D will move exactly at the time required, thus causing
the admission valves to open and the discharge valves to
close in the reamer required to give the best results.

The use of a special gear for operating the valves greatly
simplifies the compressor, as instead of a large number
of small valves only one inlet and one discharge valve ar«
required. All the valve gear is upon the outside, where
it is easily accessible for adjustment and attention.

Automatic Governor. — Frequently the demand for air is
of such an intermittent character that it is of great import-
ance to automatically govern the speed of the compressor
according to the quality of air required. This regulation
is an important feature of the " Daw " compressor, and is
automatically effected by a specially-devised air pressure
regulator acting in conjunction with the usual speed
governor on the steam valve gear, controlling the cut-off
mechanism and regulating the speed of the compressor from
maximum to minimum, according to the quantity of com-
pressed air required, so that the consumption of steam is
proportioned to that of the compressed air used.

SHOP TEST OF A "DAW" PATENT CLASS E CROSS COMPOUND STEAM
AND TWO-STAGE AIR COMPRESSOR.

Registered No. 112. Date : 25th November, 1903.

Dimensions of Compressor.

Low-pressure air cylinder, diameter 20^ inches.

High-pressure air cylinder, diameter 13 inches.

Low-pressure steam cylinder, diameter 24 inches.

High-pressure steam cylinder, diameter 12 inches.

Common stroke of all cylinders 30 inches.

Clearance of low-pressure air cylinder 1*12 %

Clearance of high-pressure air cylinder '90 %

Revolutions per minute during test 94

Piston speed 470 feet.

Capacity cubic feet of free air at 94 revolutions per

minute 1077

Reduction in capacity due to clearance in low-pressure

cylinder 29 c. ft.

Net capacity in free air per minute 1048 c. ft.

252 AIR COMPRESSORS AND BLOWING ENGINES.

Temperatures.

Shop temperature, Fah 65 deg.

Temperature of cooling water, Fah 80 deg.

Temperature of water jacket, low-pressure air cylinder 88 deg.
Temperature of water jacket, high - pressure air

cylinder 86 deg.

Temperature of air at exit from low-pressure cylinder. . . 215 deg.

Temperature of air at exit from intercooler 88 deg.

Temperature of air at exit from high-pressure cylinder 214 deg.

Temperature of water passing iutercooler 90 deg.

Cooling Water used.

Quantity of water passing intercooler, gallons per

hour 1490

Quantity of water passing water jacket, low-pressure

cylinder, gallons per hour 45

Quantity of water passing water jacket, high-pressure

cylinder, gallons per hour 40

Pressures.

Barometer 29'9

Initial steam pressure, pounds per square inch 140

Intercooler gauge pressure, pounds per square inch ... 21

Receiver gauge pressure, pounds per square inch 72

Steam Cylinders —

Mean pressure : High-pressure cylinder 62'3

Mean pressure : Low-pressure cylinder 11'25

Air Cylinders —

Mean pressure : High-pressure cylinder 34'85

Mean pressure : Low-pressure cylinder 15'67

Indicated Horse Powers.

Air Cylinders. Steam Cylinders.

Low pressure 73'66 Low pressure ... 72'48

High pressure ... 65'89 High pressure ... 100'35

Total ... 139-55 Total... 172'83

Isothermal power required to compress net capacity of free

pressure, viz. : 1,048 cubic feet to 72 Ib. gauge 119'47

Efficiency ratio of compression.

* «« % = ^ * 10» % = *™ %

Efficiency ratio between steam and air cylinders.

Total I.H.P. air cylinder -fl 0/ _ 139*55 Inft0/ _ 8n.7,o/
Total I.H.P. steam cylinder X °/0 = 172*8 X 10°% 8° 7°/0

AIR COMPRESSORS. 253

Efficiency of compression from atmosphere to receiver.
Isothermal air Q % 119J7 Q „ = 6913 o

I.H.P. steam 172'83

Remarks. — During the shop test the compressor was supported on
loose foundations only, and when erected in position, on solid foundations,
the efficiency between steam and air cylinders, on the known efficiency
of similar " Daw " compressors, will exceed 90 per cent, and the
efficiency of compression from atmosphere to receiver will in actual
work exceed 90 per cent of 85*61 per cent, or 77'05 per cent.

The compressor ran smoothly, and both the mechanical and air
governors acted promptly.

Types of Daw Compressors. — The Da,w compressors are
made for either single or multi-stage compression, the
compressing cylinders being disposed in such manner that
the work of the motor will be a, minimum, and according
to requirements are built in the following types : —

Direct steam driven.

Driven by oil or gas engines.

Driven by belt or rope.

Driven by water power.

Driven by electric motors.

Sectionalised for mule or manual transport.

Single Straight-line Class " E " Daw Compressor. — A
view of one of these is shown in fig, 257. The inlet and
discharge valves of the compressing cylinders are as
described ; the air cylinder is placed tandem with the steam,
cylinder. The steam cylinder has Richardson's trip gear,
which obviates the friction due to slide valves, and main-
tains the speed of the engine practically constant, whilst
giving a perfect distribution of steam under all loads.
The governing, as will be seen from the illustration, is
controlled by the automatic air-pressure regulator, in
addition to the usual speed governor.

This compressor has a free air capacity of 790 cubic feet
per minute compressed to a pressure of 80 Ib. per square
inch. The number of revolutions is 100 ft. or 550 ft. piston
speed per minute.

Gross Compound Two-stage Air Compressor with Air
Washer. — This compressor was built by Messrs. A. and Z.
Daw for a colliery in Natal, an express condition being that

254 MR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

255

they were to provide an air washer, through which all
the air was to be drawn and thoroughly washed before
entering the low-pressure air cylinder. The capacity of
the compressor is 2,500 cubic feet of free air per minute
at sea level, compressed to 90 Ib. per square inch, running
at 90 revolutions or 600 ft. piston speed per minute. The

FIG. 238.

cylinders, as in all Daw compressors, are water-jacketed,
and the air cooled between the stages, and in this way the
isothermal condition of compression is approached. The
intercooler consists essentially of a large number of tubes,
through which there is a constant flow of water, the air
being compelled to traverse across the tubes by a series
of baffle plates, by which means the air is split up and
every particle brought into intimate contact with the

250 AIR COMPRESSORS AND BLOWING ENGINES.

cooling surface of the tubes. The water for cooling and
the air which is being cooled are arranged to flow so that
the air just before it leaves the intercooler meets with the
coldest water.

The air washer designed by Messrs. A. and Z. Daw is
shown in fig. 258. It is extremely simple and remarkably
efficient. The inlet openings are protected by wire gauze,
and arranged on opposite ends of the washer to balance
any suction pressure on the surface of the water. The
air passes down through the end vertical channels, and is
distributed through five horizontal troughs over the surface
of the water in the washer. Slots are cut in the side
plates of each of the troughs, and the air, in passing
through these slots, is split up into thin streams and
thoroughly washed by the water, which normally covers
the slots to a depth of 3 in. The vertical baffle plates
arranged along the troughs are to prevent swishing of the
water, and the horizontally-inclined baffle plates are to
arrest any particles of water carried up by the air, and
as a further precaution a vertical water separator is
introduced between the washer and compressor. A sludge
cock is fitted for periodically washing out the sludge that
may accumulate.

The action of the air washer was exhaustively tested by
Geo. A. Goodwin, Esq., M.I.C.E., Wh.Sc. Hoppers were
fixed in front of the wire-gauze protected openings, and
fine coal dust fed into them, the compressor being run
at its full speed of 90 revolutions per minute for about
twenty minutes. The pipe leading the air from low-
pressure cylinder to intercooler was disconnected, and a
large clean duck bag secured thereto, through which all
the air from the low-pressure cylinder during the trial had
to pass. About IJcwt. of dust was fed into the washer,
and, so far as observation was possible, every particle was
separated in the washer, the bag being quite clean at the
end of the run. The piping was then coupled up, and a
full run of 55 minutes' duration made, during which
150,000 cubic feet of free air were drawn through the
washer, the loss of water during the run being 2 gallons,
or 1 gallon for 75,000 cubic feet of free air. A vacuum

AIR COMPRESSOBS. 527

gauge attached to the washer was not sensitive enough
to record any reduction in pressure below the atmospheric
pressure.

Altogether the run was highly successful, and most
gratifying to the designers.

Belt-driven Daw Compressor. — On fig. 259 is shown
a reproduction of a photograph of a two-stage belt-driven
compressor, the test of which is given on page 259.

Sectionalised Daw Air Compressor. — The compressor
shown on fig. 260 represents probably the most remarkable
example of sectionalised air compressor ever built, and
was built by Messrs. A. and Z. Daw for a gold mine in
Ashanti before the advent of the railway to Kumasi.

The compressor is of the direct-acting duplex type, with
a capacity of 624: cubic feet of free air per minute, com-
pressed to 70 Ib. per square inch, running at 133 revolu-
tions, or 400 ft. piston speed, per minute. Its destination
was 110 miles up country, the pathway to the mine being
for the greater part through a primeval forest, and the
difficulties of transport were so great that the limits of
weight, of each section was fixed at 80 Ib. to 90 Ib., except
for the cylinders, crankshaft, and rims of flywheels, which
parts were limited in number, and not to exceed 250 Ib.
each in weight packed. The gross weight of the com-
pressor was 15 \ tons, and wa.s carried the 110 miles inland
by 600 carriers, over rivers and through swamps, many of
which were dangerous to human life. About two months
were occupied in the transit through the bush, and the
whole was safely delivered without loss or damage to any
part. This compressor has now beeja at work for several
years, and, although built up in the remarkably small
sections above described, has worked with the greatest
smoothness and steadiness, and with complete immunity
from breakdowns and repairs.

58. Bailey's " K osier " Air Compressors. — These are
constructed by Messrs. W. H. Bailey and Company, Albion
Works, Salford, Manchester. They belong to that type
in which there is a reciprocating part or parts forming
the suction valve, and also closing the discharge passage
at the end of the stroke, but which also have self-acting

18AC

258 AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

259

TEST OF A TWO-STAGE BELT-DRIVEN AIR COMPRESSOR FOR
TERMINAL AIR PRESSURES OF 70 LB. AND 80 LB.
GAUGE PER SQUARE INCH.

Class K. Size 17 in. and 11 in. x 24 in. Date, 5th December, 1902.

Shop temperature 65 deg. Fah. Barometer 30 -2 in.

Receiver gauge pressure.

i-0

Revolutions per minute

280

104
416

116
464

88
352

Piston speed, feet per minute

Capacity, cubic feet free air per minute
Temperature of cooling water, Fah

441
56°

86°

656
56°

86°

732
56°

86°

555
56°

87°

Temperature of water jacket, L.P. cylinder.. . .

Temperature of water jacket, H.P. cylinder . .
Intercooler gauge pressure

91°
21

137°

70°

91°

2025
73°

93
21

207°
75C

98°
22

208°

72°

Temperature of air at exit from L.P. cylinder
to iutercooler

Temperature of air at exit from intercooler . . . .

Temperature of air at exit from H.P. cylinder.

206°

212°

218°

222°

Temperature of water passing intercooler

63°

65°

70°

66°

Quantity of water passing intercooler, gallons

702
33

30
28-65
27-00
55-65

702
33

30
44-30
42-00
86-30

730
33

30
50-75
47-50
98-25

730
33

38-25
37-00
75-25

Quantity of water passing waterjacket, L.P.
cylinder

Quantity of water passing water jacket, H.P.

I H P of L P cylinder ...

IHP of H.P. cylinder .

Total mean I. H.P. of air cylinders

Total isothermal power required to compress

49-56

73-74

82-27

66-22

Efficiency of the compressing process, viz. :—

Total isothermal power v 1W ^

89-06%

85-45%

83-74%

88%

Total mean I. fcl. P.

260 AIE COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSORS.

261

discharge valves, which control the movement of discharge.
The action of the valves is shown in figs. 261, 262, and

FIG. 261.

FlG.

263, which represent a double-acting cylinder fitted with
Roster's patent piston valve gear. The air enters through
a suction pipe at S. In fig. 263 the piston is moving to

262 AIR COMPRESSORS AND BLOWING ENGINES.

the left, so that air enters from S by the port C to the
right-hand side of the piston. The piston valve has opened
both ports C, C, and the air can pass without throttling.
On the left-hand side of the piston the air drawn in pre-
viously is being compressed, and when it reaches the final
pressure the valve B opens, and the air is discharged to
the delivery pipe. The piston valve A is now moving to
the left, and closes the port C exactly when the piston
arrives at the end of its stroke. As the suction stroke

FIG. 263.

on the right-hand side is completed at the same time, the
port at this end is closed at this moment, so that the
piston valve prevents communication between the left-hand
side of the piston and the discharge chamber E, and the
right-hand side and the suction space S. The piston, D
now moves in the opposite direction, and during this time
the piston valve passes through its middle position to the
left, opening the port C at the left-hand end of the cylinder
to S, and the port C at the right-hand end. The space
to the right of the piston is not connected with the dis-
charge chamber E until the pressure on the right of the
piston is sufficient to open the right-hand self-acting valve
B. It is claimed that the Roster valve gear has the follow-
ing advantages : —

AIR COMPRESSORS. 263

(1) It offers no resistance to the entrance of the air;
(2) the entering air is not heated during the suction
stroke; (3) it gives the highest volumetric efficiency; (4)
it has no defects inherent in the design ; (5) there is no
resistance to the discharge of air from the cylinder; (6)
is suitable for all speeds ; (7) noiseless ; (8) wear and tear
are reduced to a minimum; (9) and is positive, safe, and
reliable.

The self-acting valves are seated by a light spring, and
not by a difference of pressure; in fact, they seat them-
selves on an air cushion between them and the piston
valve ends. Many serious accidents and fires have been
caused by the explosion of the oil vapour from the
lubricating oil in the receivers and cylinders of air com-
pressors. These explosions are always possible with auto-
matic valve compressors, as their valves are liable to stick,
and do not seat themselves properly. The sticking of the
valve causes leakage, and some of the compressed air
flows back to the cylinder from the discharge pipe, and the
consequence is that the hot air raises the temperature in
the cylinder so much that at the end of the next com-
pression stroke it is sufficiently high to vaporise the oil,
and fire< the mixture of the gas and air. With the Koster
patent mechanically-operated valve gear the risk of
cylinder and receiver explosions is entirely eliminated in
both single and two-stage compressors.

Figs. 264, 265, 266, and 267 are sectional views of Bailey's
" Koster " two-stage compressor, while fig. 268 shows
indicator diagrams. In fig. 264 the differential air piston
P is actuated by the connecting rod R ; the piston air valve
by means of the eccentric 0 and rod S. Free air is being
drawn through the suction opening A, and passes through
the port B to the cylinder, the piston valve C being on the
right-hand side of the port at the time. When the air
piston arrives at the end of its stroke the piston valve C
closes the port B, and on the return stroke the air drawn
previously into the cylinder is compressed. On the desired
pressure being reached, the piston valve C having some
time before opened the port B, and passed to the left-hand
side of it, the compressed air flows through the spring

264

AIR COMPRESSORS AND BLOWING ENGINES.

valve D to F. The first stage of the compression is now
completed, and the air thus compressed passes through
an intercooler to H on the high-pressure side of the

compressor. From H it passes to the 'annular space K,
the air piston moving towards the right-hand side of the
cylinder, and the piston valve L being at the left-hand side

AIR COMPRESSORS.

265

FIG. 265.

Fiu. 166.

Fro. 267.

266 AIR COMPRESSORS AND BLOWING ENGINES.

of the port I, so that in the same stroke towards the right-
hand side the air compressed in the first stage of com-
pression is discharged through port B and drawn in through
port I. On the return stroke to the left-hand side free air
is again drawn in through the port B, and the air in the
space K is compressed to the final pressure, and now passes
through I to the spring discharge valve, and into the
delivery pipe at M. A special advantage in this valve gear
must be noticed. If Corliss valves are used in place of the

FIG.

piston valve the air between the discharge Corliss valve
and the self-acting valve is re-admitted to the cylinder near
the beginning of the compression stroke, and this sudden
fall in its pressure causes a loss of efficiency; but the
piston valve C, after it has closed the port B with its
right-hand edge, continues its motion to the right, and
forces out the compressed air left between it and D through
D into F. Thus in fig. 266 the piston C is moving to the
right and discharging the air as explained, although on
its left-hand side free air is flowing through B. In fig. 267
discharge is taking place from the low-pressure side of

AIR COMPRESSORS.

267

lO
»0
<M

6
H

I I s ' I ! ! § s s

7 & 1 777S S -
S ' i 1 "

i^ — « g CO CO >^

7 1 s • * J 4 • « s . -

CO ^ CN CN

! s en s

7|i 5 4 i S ^S

? S C4 CN

CO
00

« ?* T5
S ° £

i f si j!iri^ ^=^

S oo m

o t~ oo o

J. S 1 J, J> J, « ^^

^ £ s s

3 "•••>
^ g 1 ™,

Free air per minute

2 '3 o — w
» o H •" S S)

1 1 &1 44II.J

^_^3 m -i X> — i S o«J,a) «

2 1 1 ti i s | Ja 1

III-: 11

3 g £ w Si

P HJ K a ^ -

268

AIR COMPRESSORS AND BLOWING ENGINES.

the piston, and suction on the high-pressure side. The
reciprocating valve has a guide N, which is fitted with
spring rings. The two piston valves work in fitted liners.
The piston and spring valves are very accessible, separate
covers being provided for access to each spring valve; no
other part need be removed. The water jacket completely
surrounds the reciprocating piston, the cylinder head, and

Fio. 269

the air valve chest. The cooling water in the jacket also
circulates through the intercooler. The cooling of the
high-pressure side is particularly effective, as the inner or
high-pressure side of the piston is always in contact with
the external air, and the water-jacketed surface is very
large compared with the annular volume. The intercooler
is mounted on the top of the machine (fig. 269) in the most
accessible position. All sizes are suitable for pressures

AIR COMPRESSORS.

269

from 70 Ib. to 150 Ib. per square inch, and are proportioned
for continuous working at the latter pressure. In the
smaller sizes the cylinder and frame are cast in one piece.
The whole arrangement, being very rigid and compact,
requires very small foundations and very little attention.

FIG. 270.

The bearings are of the very best metal, and of generous
proportions; lubrication is automatic and continuous, the
supply to the bearings being on the ring principle, and
to the other parts of the machine from adjustable sight-
feed lubricators. The leading dimensions of these com-
pressors are given in the table on page 267.

270

AIR COMPRESSORS AND BLOWING ENGINES.

Figs. 270 and 271 show vertical belt and electrically-
driven two-stag© air compressors. Messrs. Bailey and Com-
pany claim that this type ia lighter and more compact than

any other compressor made. All sizes have water jackets
and intercoolers. The working parts are enclosed and dust-
proof. It is very suitable for arrangement as a portable
plant in combination with a steam, oil, or electro motor.

AIR COMPRESSORS.

271

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272

AIR COMPRESSORS AND BLOWING ENGINES.

It is extensively used for starting large gas engines, raising,
stirring, and cooling liquids, working pneumatic tools and
machines,' blowing dust out of dynamos and motors,
inflating and testing rubber goods, etc.

The table on page 271 gives leading dimensions (figs. 270
and 271.

Figs. 272 and 273 show a compound tandem two-stage
air compressor by the same firm, and similar engines with
only one steam cylinder are also constructed by this firm.
Fig. 272 is a general view, and fig. 273 an elevation and
sectional plan. The compressing cylinder has been already
described; the high-pressure steam cylinder is fitted with
equilibrium double-beat lift valves, with coiled spring
closure cushioned by oil dashpots. The low-pressure is
fitted with similar valves or Corliss gear. The high-
pressure valve gear is driven from a cross shaft by
eccentrics, is controlled directly by the governor, and is
fitted with a disengaging motion. Admission is from 0
to 70 per cent. The governor is designed to control the
speed or the capacity. The number of revolutions is
adjustable by hand between large limits. If desired, it can
be arranged to regulate the speed automatically, and to
stop the engine when a certain speed is reached. The
following table gives the leading dimensions of two sizes
of this type : —

TWO-STAGE COMPOUND AIR COMPRESSOR. FIGS. 272 AND 273.

Free air per minute, in cubic feet

808-6
25-00
20-27
12-8
20-67
21-65
145

150 to 160

1059-3
28-14
22-83
13-80
22-44
23-62
140

195 to 209

Diameters of differential pistons

larcrp

„ ,, ,, small
Diameters of steam cylinders high-pressure
j, ,, ,, ....low-pressure.
Length of stroke

Revolutions

B.H.P. required in steam cylinders
air pressure

for 90 Ib.

19AC

276

AIR COMPRESSORS AND BLOWING ENGINES.

Fig. 274 shows a cross-compound two-stage compressor.
The leading dimensions of this type are given in the follow
ing table : —

CROSS-COMPOUND TWO-STAGE Am COMPRESSORS.

Free air

per
minute.

Diameters of
air cylinders.

Diameters of
steam
cylinders.

Length of
stroke.

Revolu-
tions per
minute.

Brake horse
power required
in steam cylin-
ders for 90 Ib.
air pressure.

950

19-68

12-40

14-56

22-44

27'56

110 163—173

1180

22-05

13-78

15-75

24-60

29-52

100

216-230

1765

26-57

16-73

18-70

29-13

33-46

320—337

2365

29-52

18-70

2067

32-50

37-40

415—445

3000

83-46

21-06

23-62

37-00

41-39

530—570

3650

35-8

22-63

25-00

39-37

45-27

640—685

4410

38-39

24-21

26-57

42-32

49-23

770-825

5420

42-32

26-57

29-13

46-26

53-16

68 950—1010

6700

48-23

30-51

33-46

52-75

53-16

65 1175-1245

59. Express Compressors* — Probably the greatest
improvement in compressor valves has been made by Pro-
fessor Stumpf, because with these a very high speed is
obtainable, and consequently the size of compressor for a
given power is much reduced. These valves open inwards
in the opposite direction to the flow of air, and are closed
by the piston in the same direction as that in which the
air is flowing. These are undoubtedly mechanically-con-
trolled valves, but special gear to work them is dispensed
with; the valve piston, whose duty it is to open the valve,
also forms an air cushion, and during the opening supplies
the necessary pressure, and controls the acceleration and
retardation of the mass of the valve, and acts as a vacuum
brake at the commencement of closing. Other
mechanically-controlled valves are too complicated for

* " Kompressoren," by A. Riedler.

AIR COMPRESSORS AND BLOWING ENGINES.

AIR COMPRESSOR?.

270

small compressors, for which there is increasing demand.
Figs. 275 and 276 show a small compressor of 270 mm.
diameter (10'63 in.) and 350 mm. stroke (13'8 in.) con-
structed for experimental purposes by A. Borsig, in
Berlin-Tegel, and tested in the engine laboratory of the
Berlin Technical High School. The compressing cylinder
is bolted to the guide casting at one end, and the steam
cylinder at the other. Behind the steam cylinder are
the crank-shaft bearings, cast in one piece with the

Centre

Fio. 277

cylinder cover. The crank is driven from the piston
rod by a crosshead and two connecting rods. The steam
valves are driven by a gear whose centre lines are shown
in fig. 277, from which its action will be readily under-
stood. Its action is the same as that of two eccentrics,
one having a small angle of advance driving the distri-
bution valve, and the other having an angle of advance
of 90 deg. driving the expansion valve.

The suction valves are Corliss, and are driven by a
return crank, connecting rod, and crank arms (fig. 275).
The opening of the discharge valves, which are " express

280

AIR COMPRESSORS AND BLOWING ENGINES.

valves," is effected by the pistons at their outer ends, and
their closing by the compressing piston, in which there are
springs to lessen the shock of contact. The air from the
compressing cylinder passes through the centre of the
valve to the back of the piston, and when it has risen
slightly above the discharge pressure, it opens the valve;
the escape of the air at the back is controlled by a screw

Fio. 278.

(fig:. 279), so that an air cushion is formed. When the
piston closes the valve, the other side now forms the
air cushion, the air escaping through the small holes
at the right-hand end of the valve (fig. 279j. The springs
in the piston were compressed 1 J mm. when the piston was
at the end of the stroke. Satisfactory diagrams were
obtained up to 200 revolutions per minute; they had
all, however, a sudden rise of pressure at the commence-
ment of discharge, after which the pressure fell to that

AIR COMPRESSORS

281

at the end of discharge, which was also the same as
that in the receiver. Fig. 281 shows two diagrams at 50 and
160 revolutions, and i atmospheres pressure by gauge.

FIG. 279.

The size of the valves was fixed for 120 revolutions,
and it was not surprising to find that at speeds above

Fio. 280.

150 revolutions suction was noisy, and the diagrams
showed a considerable fall of pressure below that of the
atmosphere.

282

AIR COMPRESSORS AND BLOWING ENGINES.

In order to study the. motion of the discharge valves
during these experiments!, diagrams of valve motion \vere
taken by connecting the valves directly with the pencil of
an indicator, as the valve stroke was less than that of
the indicator piston. The valve motion is shown by the
ordinates (fig. 282), and the abscissae are proportional
to the stroke of the piston. A series of diagrams were
taken in which the resistance of the air cushion TV as
varied to suit the revolutions. These are shown in fig. 283
the figures annexed to the curves denoting the revolutions.
It will be seen that up to 60 revolutions the velocity with

FIG. 281.

which the valve opens is uniform. Above this speed,
however, the line of opening is curved, showing that the
air cushion acts more effectively towards the end of the
valve stroke, and the opening increases with the speed.
At a constant speed, by increasing air cushioning, the
opening of the valve is reduced. In none of these experi-
ments could any irregular motion of the valve be noticed.
Diagrams were also taken at 50 to 200 revolutions with
very little air cushioning. All of these showed at first
a uniform velocity of opening, which fell off towards
the end, and a quick closing with uniform velocity shortly
before the end of the stroke. Fi<_>-. 284 shows similar
diagrams in which the drum of the indicator was not
connected to the piston rod, but was driven by an
eccentric in such a manner that when the valve closed

AIR COMPRESSORS.

283

the indicator drum was moving at a high speed. The
opening curve is now on the right and the closing on
the left, and the valve was not acted on by the piston
during the last 3 mm. of its motion when closing. The
closing curve shows the rapidity with which the valve

n- 120

n-so

f) • ZOO

FIG. 282.

is partially closed by the piston, and the slowness with
which the closing is completed automatically after the
dead centre has been passed.

These diagrams were taken at various revolutions, and
showed that the higher the speed the sooner after the
dead centre was the valve closed. Diagrams were also
taken in this way when the valve was mechanically
controlled during its whole closing stroke. The closing
takes place shortly before the dead centre, and at high
speeds the valve re-opens again slightly and closes again

284

AIR COMPRESSORS AND BLOWING ENGINES.

before the dead centre is reached. This, however, is not
noticeable in the compressor diagram. This is an illus-
tration of the experimental work done in German technical
schools, which differs somewhat from the testing of toy

Fio. 283.

cranes and jacks, anl the measurement of the kinetic
energy of toy flywheels and the like, which is now recom-
mended for English colleges.

FIG. 284.

As a comparison between equivalent sizes of compressors,
the three orank engines at the Quai de la Gare, Paris, are
12'2 metres high, and take up a floor space of 11'5 by 6'15
metres. An equivalent express compressor would be 5' 7

AIR COMPRESSORS.

285

Fia. 285.

286

AIR COMPRESSORS AND BLOWING ENGINES.

metres high, and take up a floor space of 7'1 by 5'3.
Fig. 285 shows the cylinder and cover of a large blowing-
engine fitted with express delivery and Corliss suction
valves. Gas power for blowing engines is coming into
fashion, and high speeds are necessary if the power of
the gas is to be used efficiently, and for this reason express
valves have been much used.

INDEX.

Air Compressor : —

Allis -Chalmers Co.'s, 1&6.

Bailey's " Koster," 257.

Boreas, The, 176.

Brotherhood, 178.

Castellian, by the Breitfeld Danek

Co., 240.
Daw, 245-257.
Daw, Belt-driven, 257.
Daw, Sectionalised, 257.
Delivery Valves, by the Gutehoff-

uung Shlitte, 167.
Duncan, Stewart, and Co.'s, 132.
Elwell and Son's High-pressure, 191.
Express, 276.
Francois, 214.
Humbolt, 172.
Ingersoll-Sergeant, 143.
King Riedler, Double, 197.
Koster, Bailey's, 257.
Kryszat, 134.t
Reavell, The, 150, 159.
Reurnaux, Test of, 31.
Richardson, Westgarth, and Co.'s,

222.

Riedler, Test of, 33.
Schaffer and Budenberg's Kryszat,

134.

Sentinel, Alley and MacLellan's, 182.
Suction and Delivery Valves, by the

Friedrich Wilhelm Hiitte, 124.
Tilghman's Patent Sand Blast Co.'s,

128.

Worthiugton Pump Co.'s, 228.
Air Compressor Valves : —

Davey, Paxman, and Co.'s, 146.
Guttermuth's, 170.
Hughes and Lancaster's, 224.
Air Compressors, Compound, 18.
Air Compressors, Compound, Bailey's

Koster, 272, 276.
Air Compressors, Compound, Breitfeld,

Danek Engineering Co.'s., 232.
Air Compressors, Compound, Daw, 251.
Air Compressors, Compound, Duncan,

Stewart, and Co,'s., 132.
Air Compressors, Compound, Phila-
delphia Engineering Co.'s, 206.
Air Compressors, Compound, Reavell,
The, 153.

Air Compressors, Compound, Schneider
and Co.'s, 215.

Air Compressors, Compound, SchUchter-
mann and Kremer, 138.

Air Compressors, Two-stage, Bailey's
Koster, 259.

Air Compressors, Two-stage, The Reavell
159.

Air, Cooling of, 16.

Air Efficiency, 5.

Air, Horse Power Required to Compress
26.

Air, Physical Properties of, 1.

Air Washer, The Daw, 255.

Air, Work Required to Compress, 2.

Alley and MacLellan's Boreas Air Com-
pressor, 176.

Alley and MacLellan's Sentinel Air Com-
pressor, 182.

Allis-Chalmers Co.'s Air Compressor
Cylinder, 196.

Bailey, W. H. and Co., "Koster" Air

Compressors, 257, 276.
Berlin Technical High School : Experi-
ments on Express Valves, 279.
Bessemer Blowing Engines, 114.
Bessemer Blowing Engines : Breitfeld,

Danek, and Co., 116.
Bessemer Blowing Engines : Kolnische
Maschinenbau-Actien-GesellschaftllG.
Bessemer Blowing Engines : Schneider

and Co.'s, 120.

Blast Furnace Blowing Engines, Effi-
ciency of, 111.
Blowing Engines, 44.
Blowing Engines, Bessemer, 114.
Blowing Engines, Blast Furnace : —
Breitfeld, Danek, and Co., 54, 80.
Efficiency of, 111.
Elsadsischen Maschinenbau-Gesell-

schaft, 98.

Friedrich- Wilhelm Hiitte, 78.
Guttehoffnungshiitte, 74.
Kolnische Maschinenbau - Actien-

Gesellschaft, 109.
Lang, 44.

Siichsischen Machinenfabrik, 01.
Schneider and Co., 67.

288

INDEX.

Blowing Engine, Compound : —
Davy Bros. , 101, 103.
Lillieshall Co., 99.
Boreas Air Compressor, 176.
Borsig Experimental Compressor with

Stumpf Valves, 276-285.
BreitfeJd, Danek, and Co. : —

Blast Furnace Blowing Engine, 54, 80.
Blast Furnace Blowing Engine, Test

of, 60.

Cross-compound Two-stage Com-
pressor, 232.
Diagrams from Bessemer Blowing

Engines, 116.
Brotherhood Air Compressor, 178.

Central Power Station, Paris, Test of a

Riedler Compressor at, 33.
Chicago Pneumatic Tool Co.'s Com-
pressor, Test of, 33.
Cincinnati Gear Compressor, Indicator

Cards from, 231.
Clearance, Effect of, 7.
Compound Air Compressors, 18.
Compound Blowing Engine :—
Davy Bros., 101, 103.
Lillieshall Co., 99.
Compression : Quantity of Heat that

must be Withdrawn, 13.
Compression, Rise of Temperature

during, 13.

Compression Curve, Exponent of, 17.
Cooling of Air, 16.
Corliss Valve, Glandless, Hughes and

Lancaster's, 224.

Crewe and Davy's Radial Trip Gear, 114.
Cvlinder Air Compressor, bv Allis-

Chalmers Co., 196.
Cylinders, Ratios of, 24.

Davey, Paxman, • and Co.'s Air Com-
pressor Valves, 146.

Davy Bros.' Compound Blast Furnace
Blowing Engine, 101, 103.

Daw Air Compressor, 245.

Daw Air Compressor, Test of, 251.

Daw Air Washer, 255.

Daw Discharge Valve, 246.

Daw Governor, 251.

Daw Inlet Valve, 246.

Delivery Valves: Guttehoffnungshutte,
Oberhausen a. d. Ruhr, 70, 167.

Duncan, Stewart, and Co.'s Vertical
Compound Air Compressor, 132.

Effect of Clearance, 7.

Efficiencies, Total and Volumetric, 5.

Efficiency, Air, 5.

Efficiency of Blast Furnace Blowing
Engines, 111.

Elsadsischen Maschinenbau-Gesellschaft
Vertical Blast Furnace Blowing En-
gine, 98.

Elwell and Son's High Pressure Air
Compressor, 191.

Equalisation of Pressure at Both Sides
of the Piston at the End of Stroke, 10,
222.

Equalisation of Pressure, Valves for Pro-
ducing, 39.

Equalisation of Pressure, Work done per
Stroke with, 12.

Experiments on Express Valves, 279.

Experiments with Compressors, 31.

Exponent of Compression Curve, 17.

Francois : Air Compressor, 214.
Fraser and Chalmer's King Riedler
Compressor at the Powell Duffryn
Collieries, 197.
Friedrich-Wilhelms Hutte :—

Blast Furnace Blowing Engine, 7S.
Suction and Delivery Valves, 125.

Gas Engine and Blowing Cylinder, Kort-

ing Double-acting, constructed by the

Siegeiier Maschinenbau-Actien-Gesell-

schaft, 84.
Governor, Air and Speed, Whitmore's,

203.
Governor of Schneider Blowing Engine,

69.

Governor, The Daw Automatic, 251.
Goodwin's Test of the Daw Air Washer,

256.
Gutehoffnungshiitte Delivery Valves, 70,

167.

Gutehoffnungshiitte Blast Furnace Blow-
ing Engine, 74.
Guttermuth's Spring Clack Valves, 170.

Heat to be Withdrawn during Com-
pression, 12.

High-pressure Air Compressor, Elwell
and Son's, 191.

Horse Power Required to Compress Air.
Table, 26.

INDEX.

289

Hughes and Lancaster's Glandless Corliss
Valve, 224.

Humbolt Air Compressor with Gutter-
ninth Valves. 172.

Indicator Diagram from Tilghman's
Patent Sand Blast Co.'s Compressor, 15.
Ingersoll-Sergeant Compressor, 143.

Kennedy's Inlet Valve, 100.
King- Riedler Compressor, 197.
Kolnische Maschinenbau-Actien Gesell-

schaft Blast Furnace Blowing Engine,

109.
Kolnische Maschinenbau-Actien Gesell-

schaft Bessemer Blowing Engine, 116.
Korting Double-acting Gas Engine and

Blowing Cylinder, constructed by the

Siegener Maschinenbau- Actien-Gesell-

schaft, 84.

Koster Air Compressors, 257, 276.
Koster Piston Valve Gear, 261.

Lang Blast Furnace Blowing Engine, 44.
Lilleshall Co., Compound Blowing En-
gine, 99.
Loss of Pressure in Pipes, 27.

Matthewson's Valves, 128.

Mechanically-controlled Valves for Air
Compressors, Philadelphia Engineer-
ing Co.'s, 209, 211.

Mechanically-controlled Valves for Air
Compressors, Schneider and Co.'s, 215.

Offenbach Power Station, Test of a
Straad Compressor at, 32.

Philadelphia Engineering Co.'s Com-
pound Air Compressor with Mechanic-
ally-controlled Valves, 206.

Physical Properties of Air, 1.

Pipes, Loss of Pressure in, 27.

Powell-Duffryn Colliery, King Riedler
Compressor at, 197.

20AC

Pressure, Equalisation of, Valves for Pro-
ducing, 39.

Pressure, Equalisation of, Work Done
per Stroke with, 12.

Pressure, Loss of, in Pipes, 27.

Pressure on both Sides of Piston at End
of Stroke, Equalisation of, 10.

Properties of Air, Physical, 1.

Ratios of Cylinders, 24.
Reavell Air Compressor, The, 150.
Reavell Compound Compressor, 153.
Reavell Two-stage Compressors, 159.
Reumaux Compressor, Test of, 31.
Reynold's Discharge Valves, 100.
Richardson, Westgarth, and Co. 'a Air

Compressor, 222.
Riedler Compressor, Test of, 33.
Riedler-Stumpf Discharge Valves, 84, 85.
Riedler Valves, 201.

Sachsischen Maschinenfabrik, Blast Fur-
nace Blowing Engine, 61.

Schiiffer and Buclsnberg's Air Compressor,
134.

Schneider and Co.'s Air Compressor with
Mechanically-controlled Valves, 215.

Schneider and Co.'s Bessemer Blowing
Engine, 120.

Schneider and Co.'s Blast Furnace Blow-
ing Engine, 67.

Schneider and Co.'s Blast Furnace Blow-
ing Engine Governor, 69, 70.

Schneider and Co.'s Valves, 122, 215.

Schiichtermann and Kremer's Compound
Air Compressor, 138.

"Sentinel" Air Compressor, 182.

" SentinelJunior " Air Compressor, 190.

Siegener Maschinenbau Actieii Gesell-
schaft, Korting Double-acting Gas
Engine and Blowing Cylinder, 84.

St. Pankraz Mine, Brietfeld Two-stage
Cross-compound Compressor at, 239.

Straad Compressor, Test of, 32.

Stumpfs "Express" Valves, £76.

Table of Horse Power Required to Com-
press Air, 25.

Temperature during Compression, Rise
of, 13.

Test of Breitfeld Danek and Co.'s Blow-
ing Engines, 60.

Test of a Daw Cross-compound Two-stage
Compressor, 251.

290

INDEX.

Test for a Koster Two-stage Belt-driven
Air Compressor, 259.

Test of a Reumaux Compressor, 31.

Test of a Riedler Compressor, 33.

Test of a Straad Compressor, 32.

Test of a Two-stage Compressor, by the
Chicago Pneumatic Tool Co., 33.

Tilghman's Patent Sand Blast Co.'s Com-
pressor, Indicator Diagram from, 15.

Tilghman's Patent Sand Blast Co.'s Air
Compressor, 128.

Total and Volumetric Efficiencies, 5.

Valve Diagrams, Stumpf "Express," 282.
Valves :

Bio wing Engines, Best number of, 52.

Davey, Paxman, and Co.'s, 146.

Daw Inlet and Discharge, 246.

Discharge, The Daw, 246.

Express, 276.

Friedrich-Wilhelm-HUtte, 125.

Glandless Corliss, Hughes and Lan-
caster's, 224.

Valves — continued.

Guttermuth's, 17.

Gutehoffnungshiitte, 70, 167.

Inlet, The Daw, 246,

Kennedy's, 100.

Koster, 261, 263.

Matthewsou's, 128.

Riedler, 201.

Riedler-Stumpf, S4, 85.

Reynold's, 100.

Schneider and Co.'s Mechanically-
operated, 122.

Stumpf Express, 276.
Valves for Producing Equalisation of
Pressure at End of Stroke, 39, 222.

Whitmore Air and Speed Governor, 203.
Work Done per Stroke with Equalisation

of Pressure at End of Stroke, 12.
Work Required to Compress Air, ?.
Worthington Pump Co.'s Air Compressor

OF THE

UNIVERSITY

JOHN HEYWOOD LTD., Excelsior Printing and Bookbinding Works, Manchester.

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