Effects of knocking on the performance and emissions of a single cylinder SI engine fueled with a fuel blend of iso-octane and aromatic hydrocarbons

Abstract

This study investigated the effects of knocking on the performance and emissions of a single cylinder port fuel injection spark-ignition engine. Three types of hydrocarbon compounds were used as fuels in this study: iso-octane, aromatic hydrocarbons, and a mixed fuel composed of iso-octane and aromatic hydrocarbons. The ignition timing was varied to investigate the effects of fuel composition and knocking from 10° to 40° before top dead center. The experimental results indicated that as the fuel evaporation improved, the ignition delay and combustion duration were shortened. Additionally, the knocking of fuels with these characteristics occurred earlier than the other fuels, and the knocking intensity of these fuels was stronger. A fuel with a greater iso-octane content improved the engine performance, including the brake mean effective pressure (BMEP) and brake thermal efficiency (BTE), better than a fuel containing a greater content of aromatic hydrocarbons. The intensity of the knocking increased as the ignition timing was advanced, thereby causing a decrease in the BMEP and BTE. Additionally, the knocking intensities of fuels with high iso-octane contents were weaker than the other examined fuels. There were no significant changes in gaseous emissions, including the total hydrocarbon and NOx emissions when knocking occurred. However, particulate emissions sharply increased as the knocking intensity increased.