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This paper presents an analysis of the mass fraction burn (MFB) of an imitated low BTU gasification gas used as fuel in a four-stroke, single cylinder, direct-injection (DI), spark-ignition (SI) gas engine. The composition of the gas is 19% H2, 30% CO, 5% CH4 and balance of N2 with a lower calorific value of 7.67 MJ/Nm3. It is aimed at studying the combustion characteristics of the fuel for possible replacement to fossil fuels in the latest engine technology. The engine is operated at wide open throttle position at lean operation condition. Pressure reading from the engine cylinder by Kistler Piezoelectric pressure transducer is used to analyse the MFB with the help of Rassweiler-Withrow model. The result showed that the MFB function of low BTU gasification gas at ultra-lean operation deviated from the normal S-curve, experiencing a double-Wiebe function with a plateau shape at around 50 to 60% of the MFB for all speed ranges studied.

This paper compares the characteristics of combustion of CNG by the pilot homogeneous charge compression ignition of gasoline and combustion of stratified, overall lean SI combustion of CNG. Homogeneous charge of gasoline is created by injecting the fuel in the manifold and the charge is heated by an air heater in order to achieve HCCI combustion of gasoline that ignites the direct-injected and stratified CNG at 80 BTDC. The combustion characteristics obtained are compared with that of CNG by spark ignition. The results show that there are significant effects on combustion characteristics, HC, CO and NO emissions. HCCI combustion has higher fuel conversion efficiency compared to SI and less emissions within certain range of loads.