Study on the combustion characteristics of acetone/n-heptane blend and RON50 reference fuels in an HCCI engine at different compression ratios

In this study, the effect of acetone fuel on combustion, operation range and exhaust emissions in an HCCI engine was investigated experimentally. An HCCI engine, which is converted from a spark-ignition engine was used in experiments. The compression ratio of the single cylinder engine, which is equipped with a port fuel injection system, can be varied. The study was carried out at compression ratios of 11, 12 and 13 and different lambda values. The high octane number of acetone was reduced to 50 by blending it volumetrically with n-heptane. The reference fuel which's octane number of 50 was used as well for comparative analysis in the experimental study. The HCCI engine was operated between 800 and 1800 rpm engine speeds, at constant 350 K intake air inlet temperature. The effects of acetone on cylinder pressure, heat release rate, the start of combustion, combustion duration, CA50, indicated thermal efficiency, maximum pressure rise rate, coefficient of variation of indicated mean effective pressure, hydrocarbon and carbon monoxide emissions were examined at different compression ratios. The highest in-cylinder pressure was obtained as 71.16 bar in the use of acetone fuel when lambda was 2.2 and compression ratio 13. Indicated thermal efficiency was recorded over 40% in ideal operating conditions. In addition, acetone extended the HCCI operation range at high compression ratios. The highest carbon monoxide and hydrocarbon emissions were obtained as %0.264 and 557 ppm in the use of RON50 fuel respectively when lambda was 2.4 and compression ratio 11.