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RATE OF COMBUSTION

AND DRAFT PRESSURE FOR A STOKER

APPLIED TO 350 H. P. STERLING BOILER

BY

J. R, LEVALty W. L. JUTTEMEYER

p, E. WlLtSON

ARMOUR INSTITUTE OF TECHNOLOGY 19 15

621. 183

I 51

lilinois Institute

of Technology

UNWERSyTY LIBRARIES

AT 379

Levally, J. R. Relation between rate of combustion and draft

For Use In Ubranf (Wy

ILLINOIS INSTITUTE OF TECHNOLOGY PAUL V. GALVIN LIBRARY 35 WEST 33RO STREET CHICAGO, IL 6061^

RELATION BETWEEN RATE OF COM- BUSTION AND DRAFT PRESSURE FOR A CHAIN-GRATE STOKER APPLIED TO A 350 H. P. STERLING BOILER

A THESIS

PRESENTED BY

JOHN R. LEVALLY

WALTER L. JUTTEMEYER

HUBERT E. WILLSON

PRESIDENT AND FACULTY

OF

ARMOUR INSTITUTE OF TECHNOLOGY

FOR THE DEGREE OF BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING

HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN

MECHANICAL ENGINEERING

MAY 27, 1915

•^YA^^^^y^^^^^

^5T

TABLE Oi' COUTKNTS.

Page,

Bi"bliography 20.

DimensioriS and Proportions .........*• 7«

Discription o£ Boiler and Setting .... 2«

DiacusBion l8*

Introduction !•

Installation and Precautions 9*

Prcpceed Method o£ Procedure 14-.

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,§ .......... enot^iJBOfit'i bna notfsLL&fenJ

-1-

IFTROBUCTIOK There has been Taut little or not attempt made to discover Just what the relation "between the rate o£ combustion and draft pressure in a furnace really is, and no authentic data has as yet been compiled.

It was with the above idea in mind that this thesis was started No attaacpt A^as to have been made tc acciunulate data whereirom an accurate heat balance might have been con- structed, but simply to find what infulenoe the draft and thickness of fire really had upon the rate of combustion.

However, after all apparatui? ha* been installed, the coal was of such a mixed variety of sizes and kinds, and there being no call for steam, the attempt was abandoned.

The enclosed report is then only an expression of what was really done in instal- lation of apparatus and a proposed method of procedure for some one to follow for the actual detsimination*

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-2-

DESCRIPTION 01 BOILER AWD SETTIFO

The teste were to have "been made upon one c£ a "battery o£ five located at the Axaioux Institute of Technology, at Chicago, Illinois. The boiler is of a Sterling type and consists mainly of three upper, or steam drums, and a large lo'ver mud drum. These sets of drums are connected "by 3-1/4" inch, lap welded, mild steel tu"be8. The tu"bes are bent at the ends in such a way that they enter the drums radially. The drvims are constructed of the best quality of flange steel, and are 3 feet 6 inches in diameter by 12 feet in length. Two hundred-fifty water'^ tubes, and twenty nine tubes afford a heating surface of approximately 3500 square feet. "Raffle^ suitably placed, on the tubes direct the flow of the heated gases 80 that they pass up the first pass, down the second, and across the third pass.

Water for the boiler is fed into the upper rear dnaui which is the coolest part of the boiler and flows to the bottom mud drum. The steam is taken from the middle upper drum.

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-5-

Two safety valves are also placed on the dmm and are set to release at 150 pounds gauge pressure. The valves are piped to the atmosphere. The Id low o££ valve is located at the hottom of the mud drumo A manhole placed in the ends o£ the three drums for the purpose of permitting inspection and cleaning.

The whole comlDination is enclosed hy a 'brick setting. I^or the dimensions of setting see "dimensions and proportions," The upper drums rest upon wrought iron "beams. These ■beams are in turn supported "by wrought iron colu/nns whose hases are set in cast iron foundations. The weight of the lower dxvm is carried hy the tubes connecting it to the steam drums. This arrangement allows the entire mass to move with the contraction and ex- pansion of the metal due to the heat*

Two fire doors are cut through the hrick work to permit inspection of the fire in the furnace aid over the "bxidgs wall.

-^-

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-4

A fire taick arch projects to vvithin one foot of the front row of tubes. This arch "be- comes incadescent from the heat that it has absorbed, and ignites the green fuel, as the fuel comes into this region.

The grate employed, is the one manu- factured by the Green Chain Grate Company. For dimensions of grate, see "dimensions and proportions".

Coal is shoveled into the hopper irhich extends across the full v^idth of the grate. The depth of the fire on the grate is regulated by means of an adjustable sheet iron gate. Raising or lower this allows more or less coal to pass into this ignition zone, and also serves to keep a constant depth of coal on the grate.

Draft is produced by means of a one hundred- seventy five foot brick chimney. The diimney is connected to the furnace by a sheet metal breeching. / damper l placed in this breeching serves to regulate the drsift in the iUrnace. It may be opened

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-5-

or closed I'xom the boiler room floor "by releas- ing the wires that hold the damper in position.

The feed water £rom the returns o£ the heating system is piped to a surge tank, From this tank the water is pumped through a yen- turi meter, constructed "by The Builders Iron -Se Foundry Co., to the rear drum ol the boiler. The height o£ the water in the "boiler is deter- mined "by the use o£ the ordinary water column.

The chain grate stoker is operated by a three horse power vertical steam engine belted to ^ Jack shaft. This shaft is connected to a rocker arm by means of an eccentric rod and a slip connection. The rocks r arm is furnished with a ratchet working on a ratchet wheel. The ratchet ^eel is connected to the axis of rotation of the grate through the ordinary reduction gearing. The speed of the grate is regulated by throttling the engine, or by changing the effective length of the rocker aim.

Coal is \mloaded from the cars into bins, and thenee gravitates to the boiler room floor.

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• iia£ T*;3iooi eric^ io iiSt\ael efiJoexi© sirfi «rii^jj;.jio

-6-

It is shoveled into the hopper o£ the stoker Toy hand.

The ashes drop into a pit under the grate and are removed "by hand.

sriS 7£baw *i:cf £• c-*rii qcib eerfer. sxlT

DIMMSIOilS AST) PROPORTIOHS .

BOILER.

-7-

Type o£ boiler , Dlamstar o£ shell, Length or shell > Thlclcnass o£ shell , Thioicnsss o£ head , Bumhar o£ tubes ,

Water tube . 42.00 inches . 12.00 £eet« 9/16 Sc 7/16 inches 5/8 & 5/4 inches. 279

Diameter o£ tubes ,( inside) 5.25 inches .

Diaaetar o£ tubes, (outside) 5 •79 inches.

Length o£ tubes ,(over beading) 18 feet ^ inches .

Steam taken dirsctly from central drum .

Kind of grata , Green C!hain Grate Stoker .

Size of grate ^ Width 9 ft, Length 9 ft. 2 in.

Araa of grate surface , 82-1/2 Sq. ft.

Heating surface of boiler, 5500 sq. feet ,

Ratio heating surface to

grate surface 1 to 42.5

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BRICK BOILER SSTTIKG .

Height , 18.5 feet,

Width , 1^ feet

Length, 22 .75 feet

-8-

Sizt,

BOILISR PUMP .

7-1/2x4-1/2x10.

VEI^TURI METER , Make , Builders Iron Pdy. Co.

Size , Indicating & recording.

Diameter , (Inlet) ^' inches.

Diameter , (Throat ) 1 inch .

-c-

. ♦eel 'vi , rUbiW

. rbni: I ( tBoxn'T), aeieiaeiCr

-9-

INSTALLATIOB OF APPAB/TUS AKD PRECAUTIOFS .

A rigid inspection o£ the boiler setting was made, and all of the air leaks stopped up as tax as possilDle, The cracks in the "brick settings, and small openings along the sides o£ the grate entrance and around all connect- ions to the interior of the furnace, cemented over with fire clay» The doors to the bridge wall and grate were removed, and the opening covered with a sheet of 1/2 inch asbestos. Before putting the asbestos sheet in place, the surface axposed to the heat was covered with a thick layer of fire-proofing. This combination was then held in place over the door opening by s^iiall machine screws set into the metal frame work of the door* The adgas around the asbestos sheet were then sealed with fire-proofing. The above pre- cautions were taken to prevent air leakage as far as possible.

The asbestos covering for the door over the fire was fitted with two openings. One

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-10-

opening vraa made small enough to "be fitted with a one-half inch pipe plug. Through this opening it was proposed to insert the connection to the CO2 apparatus, to ot>ta.in the sample of gas over the fire for analysis. The second opening was ahout three inches, high , by four inches long, and was coysred "by a swinging screen of sheet mica* The sOieet of mica was sufficient in area to completely cover the opening and permit no great air leakage around the edges. Through this apparatus it was proposed to t«Uce the temper- ature of the fire, A Jery pyrometer was set up, the mica screen swung to one side for an instant, and the pyrometer focused on the fire. The temperature resulting showed on the galvanometer. The reading of the temper- ature of the fire should take place after all other vaurious readings have "been recorded^ in order to prevent air leakage.

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• e^ji^el xif :fiTS^eiq o^ lefcic nx

-n-

A Hayes C02 apparatus containing fresh solution was set up and connected to a firs foot length of quarter inch pipe "by the usual rubber tubing. The gas sample from over the fire was taken with this arrangement. A long piece of quarter inch pipe was instal- led permanently in theuptake» This length of pips was fitted for proper connection to the gas analysis apparatus, and through it a sample of the gas in the uptsdce was obtained.

Two draft gauges were installed on the wall at a convenient height, and the proper connections to the interior of the furnace over the fire .and in the uptake, were made. The connections -.rere mads ndth quaitex inch ca.Ft iron pipe. All connections were burred out, and the pipes carefully cleaned before installation. This removed all obstacles for a true reading of the draft pressure, except that which arises froni the friction in the pipes. This latter error may be neglected.

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The quality o£ the eteaff. was ohtained from the throttling calorimeter installed on main steam line leading irom the central steam drxaii. A one-half inch pipe connection was already in place just abovethe dr\im, so the calorimeter was connected at this point* / half inch glohe valve and a steam gauge with the customary "curl* for the gauge, were placed in the line leading to the calorimeter. The laigth of pipe between the calorimeter and the point of connection to the main steam line was made as short as possible. The thermometer cup was filled with a heavy cylinder oil, and a thertiometer reading from zero to three hundred degrees put in place. The pressure of the steam as indicated by the gauge at the calori- meter was taken as the tar ue boiler pressure.

Scales and baskets for the weight of coal fired were provided.

The water fed to the boiler per hour is measured by the venturi meter. A chart over the recorder k^eps a record of the water evaporated.

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• be ts-i oqsro

-13-

Several small numbered "baking powder cane were provided for samples o£ "Oae coal and refuse. It was intended to take several saoples of "both at intervals during the run, and keep them in the cane for analysis at a convenient time.

All apparatus was carefully calibrated "before its installation.

.3 t& ^is^lerts -xol srteo srft ni ^aarfJ- qf59:i fins

-14-

PROPOSED METHOD Oi PE0CM)UE3? ,

OBJECT :-

The deteimination of the relation betiveen rate o£ combustion and dralt pressure for a chain-grate stoker, APP/KATUS:-

The test will involve the installation and use of the following inetruKents'. Draft gauges over the fire and in the uptake . Throttling calorimeter and eteaan gauge . C02 Apparatus . Smoke recorder • Pery pyrometer • Speed cotinter for grate.

Scales and "baskets for weight of coal fired. Venturi meter for measuring water evaporated.

METHOD OP PROCEDURE:

The boiler should be in operation as long as possible Toefore the test is started, 17o riins should be attempted before the boiler and

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o^^f *b9txt>iB si +8s:t srfct sxolesf sX.-.ia^'oq 36

-15-

and setting have had an opportunity to

reach a xmii'orm temperature •

When the above conditions have been

satisfied, the hopper o£ the stoker should

be rilled full and then leveled off and the

run started. Take the follovring readings

every five minutes:

Average Draft, inches of water, Over the fire . In the uptake .

Average Gas Analysis , Over the fire- In the uptake .

Temperatures, degrees Fahrenheit,

Ertemal air) Average for test. Boiler room ) Tire . Steam .

Pressures ,

Parometer. True Boiler •

Weights, pounds per hour,

Water fed to boiler .(venturi meter)

Coal fired .

Sample of coal fired for later analysis .

Sample of ash for later analysis.

(Kote in log sheet kind and size of coal)

Uote Carefully ;

Thickness of fire . (Constant for run) Speed of grate, feed per minute. Droppage of fuel through grate, if any. Condition of fire ( IlIPORTAFT ) . Smoke observations (Smoke recorder)*

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^ 8eai;s«3x5

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«{ 31x1 lo noivi--, •,

-16-

Precaution must "be taJfen to provide for an ample exceee o£ air in the "boiler room. The firing of the coal should be in such a manner that the conditions at the start of the run and at the finish are the same. That is, the water should he at the same level in the "boiler, and the coal at the same level on the hopper at the finish as at the start.

The speed of the grate should be maintained as near uniform as possible, but every change in speed should be noted in the log sheet.

The observations sb regards to the condit- ion of fire should be watched very carefully. The swinging cover in the asbestos sheet provides a place where the fire may be care- fully watched with blue glasses without open- ing cover. Kotes as to whether the fire is short, even, contains holes, etc. should be made frequently.

The analyses of the gases should be carried on chiefly for the C02 content. If no C02 recorder is available, the analyses should be made at intervals not exceeding

■'DX"

,:zo(yi T?Xioo' &rii nl itf-- lo aaaoxe 3l\/.^ hb

e.-fi io v+x«5t? !?:{+ *j?- ?iToititnoo erf? c^e'-it •xeoraeji

erii as. L^-7^1 e;nE.8 &iU iR ©"f bluoris xsj-sw sr?t srfi no I«vel ease edi fs Ifloo e.ff^ br££ ,i3liocf ,.txiij-? srfi ^B sr dsinii srf^ :f£ laqqoxf fc©nlfitnx£.3i ecf bluods etE-xg e-fc^ lo bssqe srf?

ssrsBilo ■\jiS7fl Jtjo' ,3lcfi3eoq bb sczollnsj lasnt as

arf Maoris asp^^^Q erit lo etail&nB srlT

II .ine^noo SOD ^K* xol 'jXleliio no b^laxf-o

-17-

firs minutes. The C02 should not get below ten percent at any time.

Several xvmb should be made with dif- £erent kinds o£ coal, varying the depth of fire, draft, and speed of grate for each kind of coal«

Have grate exactly level, and furnish photograph showing that the gate and arch are in satisfactory condition.

Too much stress cannot be put upon the importance of keeping accurate readings and conditions of fire. All air passages except those leading through the grate must be sealed off.

.eaUj vrte c^£ -fsiaoisq .TSt -JLi fc fliiw ebea scf MiJOiie en:jx i«isvs3

ioBs -xoi e.t£a3 lo hesqe fca^a , + iBib ,eiH

aoqjj d'yq so' cJoanso ase-i^s r{o*;i2 ooT esnifcB**^ eteijjoos saicieejl io sortfiiTtoqiai e.fj- aesBaaeq -xxb £X^ ,6ail lo e^-Toi-tlbnoo bnp

-18-

Discussion

The ccoibustiorx rate curves printed in the various catalogues and magazines show the combustion rate decreasing about in pro- portion to the decrease in draft. This is probably true for a draft of more than two- tenths of an inch of water in the furnace, but it is doubtful if the combustion rate decreases as rapidly at the lower pressures. / set of tests of the aforementioned would give an accurate determination of this.

The great trouble with the diain-grate stoker is its small range of efficient operation. By varying the depth of coal on the grate, and the speed of the grate and then by means of the damper , regulating the draft pressure for each change in speed and depth ojf Jul re, the limit of efficient operation might be determined.

The lowest point of operation might be taken as that point at ^ich the grate just begins to turn red, as it comes over the water back. The upper limit is held within the capacity of the grate.

al betnixq, ^qthjo sJfia aoi^BUcfiSOo erfT vfo'ie esaisB^ei's bos b9Sj^oS.b&so ayolx^v s.it

fsi «i;ffT . *l*<:ti> ajc e3saio&b tfttt of aoltxoq ^o^t n^riS sioia lo Vlfiib .3 ^sol tun^ iLd&doiq

«*Bi ■.^ox.tst/rfffioo erf* "il l.u'if^sjob sr .*i *wrr

.39iy3aeiq -leT/oI en? ts '/IM^pi as sssssxosb

bliL'ow benox^neoistiole stit lo aiBei io Je? \

^itpioxiie lo epm»x iir-5^.R aix ?x ■X's:-[oJ-3

CIO liROo 10 iij-qsi) srfi- aniM:^^'"'' ^^ .cioxteisqo

,i)ST[I.Tns:)'sJb erf J^isinj

ill'Ulw .blftrf si +ijsil xeqqw srfT .Jio/^cf iscffi^

-19-

The perioimance o£ the "boiler and t\x3na.ce may "be expressed in terms o£ weight of water evaporated per hour per square foot of heating surface. The results should he plotted against the pounds of coal humed per square foot of grate surface.

Combining the tests would give the re- lation "between rate of comhustion and draft pressure for a chain-grate stoker.

-?i Sifi- avl-a hi 110'* aj-ss.-t f-'.-Ji ^sjaJ-.iioD.o'D *-iBX.5 £i£Te iToI ift';.fi.iOo 'xo serin m^ev; :fsrf iioi^;-!

-20-

BIILIOPBAPHY.

"Steam Power Plant Engineering", Ge"Hharclt« "Experimental Engineering," Carpenter. •Iron Age, Voiuir;e 40.

"Hand Booit lor Mechanical Engineers", Kent. "Stirling Boiler Catalogue", Stirling "^oiler Co

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