Effect of fuel structure on emissions from a spark-ignited engine

Nitrogen oxides, carbon monoxide, and hydrocarbon emissions from a single-cylinder spark ignition engine fueled with methane, ethane, propane, n-butane, isopentane, isooctane, or toluene fuels were measured. Emission profiles are partly attributable to changes in flame temperature and the hydrogen:C ratios of the diverse fuels. Both the total engine-out hydrocarbon emissions and the distribution of individual hydrocarbon pollutants in exhaust gas are sensitive to the fuel used. Ethane produces the lowest and toluene the highest hydrocarbon emissions under all engine operating conditions.