Contribution Ratio Study of Fuel Alcohol and Gasoline on the Alcohol and Hydrocarbon Emissions of a Gasohol Engine

Abstract

Methanol (CH3OH) and ethanol (C2H5OH) are generally called alcohol. They can be mixed with gasoline to fuel SI engine. The fuel blends of alcohol and gasoline are named gasohol. Alcohol emission characteristics and the contributions of fuel on hydrocarbon (HC) emission were experimentally investigated on a threecylinder, electronic controlled, spark ignition JL368Q3 engine when it ran on 10 (v/v) %, 20 (v/v) %, and 85 (v/v) % methanol/gasoline and ethanol/gasoline fuel blends. Experimental results show that, the value of alcohol emission rates (g alcohol emission per kg alcohol fuel, g/kg.) is a decreasing exponential function of exhaust temperature with high correlation; regardless of the alcohol fraction in fuel blends, the CH3OH emission rate is no more than 8%, while that of C2H5OH no more than 35%. The emission rate of nonalcohol HC was one grade higher than the alcohol emission rate; the minimum HC emission rate occurs at middle and high engine loads, it is around 40% for methanol/gasoline blends and about 50% for ethanol/gasoline blends. Gasoline is the main source of HC emission of gasohol engine, methanol contributes no more than 8% while ethanol no more than 25% on HC emission.