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Gas Air Required per Pound of Gas at 62° F Products of Combustion Hydrogen 34.8 lb. or 457 cu. ft. Water Nitrogen Carbon burned to CO2 11.6 lb. or 152 cu. ft. Carbon dioxide Nitrogen
24. The gasolines and oils in common use are composed of hydrocarbons, with sometimes a small percentage
of water and sulphur compounds. When the percentages of
C and H are known, the air required for the combustion of
1 pound of the fuel is easily found. For example, suppose
a certain oil is 90 per cent. C and 10 per cent. H. To burn
the C requires 152 × 90⁄100 = 136.8 cubic feet of air; to burn
the H requires 457 × 10⁄100 = 45.7 cubic feet of air. Hence, to
burn 1 pound of the oil requires 136.8 + 45.7 = 182.5 cubic
feet of air.
Let V = number of cubic feet of air required for combustion of a given fuel;
C = percentage of C, expressed as so many parts
in 100;
H = percentage of H, expressed as so many parts in 100.
- V = 152 × C⁄100 + 457 × H⁄100
- or V = 1.52 ( C + 3H), very nearly
Example. — A certain oil contains 84 per cent, of carbon and 16 per cent, of hydrogen; how many cubic feet of air is required for the complete combustion of 1 pound of this oil?
Solution. — According to the formula,
V = 1.52 (C + H) = 1.52 (84 + 3 × 16) = 200.64 cu. ft. Ans.
HEAT OF COMBUSTION
25. Heat Value. — The quantity of heat produced by the complete combustion of various gases and petroleum products has been found by experiment. This quantity is known as the heat value of the fuel, and represents the greatest amount of heat that can be obtained from a given quantity of the fuel by complete combustion. No accurate
