Theoretical investigation of the effects of gasoline ethanol blends on spark-ignition engine combustion and cycles

SUMMARY Theoretical Investigation of The Effects of Gasoline - Ethanol Blends on Spark - Ignition Engine Combustion and Cycles In the research studies on the spark ignition (SI) engine fuels, the aim is to improve the fuel octane level, to decrease the engine fuel consumption and to reduce the obnoxious exhaust emissions. Additionally, in recent years researchers have interested to alternative fuels due to limited crude oil reserves. The most attractive alternative fuels for SI engines are alcohols such as ethanol and methanol. Their productions are based on renewable natural energy sources and they have some relevant properties for using in engines. Properties of ethanol generally appear more favorable than those of methanol since its calorific value is higher and its latent heat is lower than methanol. The use of ethanol as a pure fuel in SI engines require some engine design modifications. It was pointed out by several researchers that blending of the certain amounts of ethanol with gasoline do not require any engine design modification. In the presented study, it was aimed that the theoretical investigation of the effects of different gasoline - ethanol blends on SI engine combustion and cycle characteristics. For this purpose a mathematical SI engine cycle model based on the first law of thermodynamics and includes a quasi-dimensional combustion model has been developed. In the presented mathematical cycle model, intake and exhaust processes have been calculated by use of a simple method. Theoretical investigation of combustion and cycle parameters of a single cylinder experimental SI engine and a four cylinder automobile SI engine fuelled with pure gasoline, pure ethanol and several gasoline - ethanol blends, have been performed. It is determined that the blends including the certain amounts of ethanol improved the engine combustion and performance. The best engine performance has been obtained with the blend including 25 per cent ethanol (by volume). Key Words: Gasoline Engines, Spark Ignition Engines, Alternative Fuels, Spherical Flame Propagation, Combustion Modelling, SI Engine Cycle Modelling, Gasoline - Ethanol Blends. VII