Investigation of combustion characteristics and emissions in SI engine fuelled with LHV gas

In this study, an experimental research on the combustion and emission characteristics of a spark ignition engine fuelled with a blended gas was performed at different engine load operations. The blended gas, which was composed by the compressed natural gas and nitrogen, was lower heating value gas. In the experiments, the parameters of combustion characteristics were analysed under 0-35% nitrogen volume fraction in the blends. The results show that the maximum cylinder pressure, the maximum rate of pressure rise and the maximum rate of heat release decrease with increasing nitrogen fraction. The flame development duration and the main combustion duration increase with the higher level of the nitrogen fraction. Meanwhile, the HC, CO emission increase and the NO(x) decreases remarkably with the increase in the nitrogen volume fraction.