Modern Mechanical Engineering Vol-I

152

FOUNDRY WORK

been made in the arrangements of tuyeres. Briefly, these usually consist
of upper and lower rows, receiving the air from the belt, and discharging it
through openings equally spaced round the circle. This disposition has
taken the place of the older method of bringing in blast through pipes into
two openings on opposite sides, which, with the low cupolas then common,
permitted a large proportion of the gases generated from the fuel to pass

/

85

i

n

tm

B

A

Fig. 56.—The " Colliau" Cupola

AF Air-belt. B, Flaring tuyeres, c, Non-conducting
space filled with sand.

Fig. 57.—" Newten" Cupola

A, Air-belt. B, Differential tuyeres. C, Drop
bottom

away out at the charging door and at the top, unconsumed within the furnace.
When carbon is burned, 14,647 B.Th.U. are given out per pound, the carbon
uniting with the oxygen to form carbon dioxide, C02. This is called com-
plete combustion. If, however, the combustion is incomplete, due to an
insufficient supply of oxygen, carbonic oxide, CO, is formed, and if this is
allowed to escape, about two-thirds of the heat is wasted, since the burning
of carbon to CO evolves only 4415 B.Th.U. The object of the upper row,
or rows, of tuyeres which have assumed bizarre forms in some designs is to