A small air-cooled gasoline engine is tested and the output is found to be 1.34
ID: 2087439 • Letter: A
Question
A small air-cooled gasoline engine is tested and the output is found to be 1.34 hp. The fuel is
liquid octane (C8H18) and it is provided to the engine at a rate of 0.15 g/s. The fuel and air both
enter the engine at 25?C. You may ignore any water vapor that enters with the air. The
combustion products are analyzed. The water in the combustion gas is removed and the
composition of the remaining components is identified. The results are summarized below.
Combustion gas analysis (after removing water).
CO2 11.4 %
O2 1.47 %
CO 2.90 %
N2 84.23 %
a.) Write the chemical reaction associated with this combustion process.
Explanation / Answer
We know there is 79% of nitrogen and 21% of oxygen in air.
For every 1 mol of oxygen there is (79/21) = 3.76 mol of nitrogen is there in air.
Chemical Reaction between octane and air:
2C8H18 + 25 (O2 + 3.76N2) --------> 8CO2 + 18H2O + 8CO + 4O2 + 94N2