4G1
OF ENGINEERING FORMULÆ.
Steam Engine.
COMBUSTION.
An ordinary furnace requires 24 lbs. of air, or 300 cube feet
of air for the consumption of each lb. of coal; by means of
fan-blast or jet of steam this quantity of air may be de-
creased to 18 lbs., or 2*20 cube feet.
From 13 to 20 lbs. of coal may be consumed per superficial
foot of fire-grate.
4 of a foot of fire-grate are required to evaporate a cubic
foot of water.
COMBUSTION OF 1 LB. OF FUEL.
Percentage of Units of Heat. Air consumed, cubic feet per lb. Relative Heat.
Carbon. Hydrogen. Oxygen.
Patent fuel 90 5-6 — 16500 163 ]02
Steam coal 89 5 •4 16200 161 100
Wallsend .. 83-5 6-7 8'2 15500 153 96
Average coal 80-4 5*1 7-6 14000 140 86
Coke .. .. 94- •04 ■1 13600 142 84
Peat .. .. 60 6 31 9900 100 61
Wood.. .. 50 6 41 7800 80 48
CONDENSATION.
The quantity cf water required for condensation Is about
20 times the amount of the feed.
SURFACE CONDENSATION.
Approximate Rule for Surface Condensers.
Area of condensing surface = heating surface x 0-7.
Tubes f in. diameter outside from 7 to 10 feet long—of
brass.
COMBINED STEAM.
Area of superheating surface = 1 square foot per indicated
horse-power.
Combined steam should not be used at a higher temperature
than 310° Fahr.
Some engineers allow 3 superficial feet per foot of water
evaporated.