Comparison of propane and ethanol fumigation of a heavy duty common rail diesel engine

A heavy duty common rail marine diesel engine operating under load on a test bench is fumigated with either propane or vaporised ethanol mixed into the inlet air at various rates. Fumigation allows the addition of moderate quantities of alternative fuels to a diesel engine without significant modification of the engine. Carbon monoxide and hydrocarbon emissions and exhaust opacity tend to increase with increasing fumigation, with larger increases for propane compared with ethanol. Cylinder pressure and the electronically controlled two stage liquid fuel injection timing are recorded with a high speed data acquisition system. At high rates of fumigation very high pressure rise rates are measured. The apparent heat release rate and the fuel injection timing together allow analysis of the mechanism of the combustion process with fumigation. For both propane and ethanol, two distinct peaks in apparent heat release rate appear when the air/fumigant mixture strength approaches the flammability limit.