This study investigated the effects of fuel composition on knocking generation and particulate matter of a single cylinder port fuel injection spark-ignition engine. Hydrocarbon compounds such as iso-octane and aromatic hydrocarbons and ETBE blended fuels were used as fuels in this study. The ignition timing was varied to investigate the effects of fuel composition and knocking from 10° to 40° before top dead center (BTDC). And equivalence ratio was changed from 0.8 to 1.2 in fixed ignition timing of BTDC 25 °CA.
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. As a result of the change in ignition timing and equivalence ratio, knocking begined when the combustion duration was shorter than 19 °CA, and the intensity of knocking increased. A fuel with higher iso-octane content at the same combustion duration has relatively high resistance to knocking.
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. BTE increased as ETBE content increased. When the intensity of knocking was 1.5 or more, BTE and BMEP decreased and BSFC increased. There were no significant changes in gaseous emissions, including the total hydrocarbon and carbon monoxide when knocking occurred. However, particulate emissions sharply increased as the knocking intensity increased. And Nitrogen oxide decreased, when the intensity of knocking was 1.5 or higher.
PN increased with increasing knocking strength. And as the equivalence ratio increased, PN increased, which is the effect of knocking. Type-1 with high iso-octane content in hydrocarbon-based fuel has the lowest knocking strength, BTE is excellent and PN is low. Futhermore, the stronger the ETBE content in ETBE blend fuel, the weaker the knocking strength and higher the BTE.