Measurement and prediction study of the effect of ethanol blending on the performance and pollutants emission of a four-stroke spark ignition engine

Considering the pollution problems and energy crisis today, investigations have been focused on lowering the concentration of toxic components in combustion products and decreasing fuel consumption by using renewable alternative fuels. The effects of ethanol addition to unleaded gasoline on the performance and pollutant emission of the spark ignition engine are established both analytically and experimentally. In the present work a quasi-dimensional model was developed to study the effect of ethanol blending on the thermodynamic cycle of the engine. The Ricardo E6/US engine has been used for verification and comparison of the results of the model with experimental tests. The results of the standard ASTM methods showed that, with increasing ethanol content, the research octane number of the blended fuels increases, while the Reid vapour pressure of the blended fuels initially increases to a maximum at 10vol% ethanol addition and then decreases. The results of the study showed that the addition of ethanol (from 0 to 30vol%) increases the engine power, thermal efficiency, and specific fuel consumption and reduces the nitrogen oxides, carbon monoxide, and hydrocarbon emissions. The ethanol added improves the combustion process, reduces the crevices flow energy, reduces the cylinder temperature, reduces the ignition delay, speeds up the flame front propagation, and reduces the combustion duration. The high useful compression ratio, which produced maximum engine power, was directly proportional to the ethanol percentage in the mixture.