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Investigation of the Influence of Spark Advance, Compression Ratio and Relative Humidity ofAir Intake on the Probability of Knock Occurrence in an SI Engine Fueled with Methane

A thermodynamic model has bee n deve loped in this paper for an SI engi ne fue led wi th methane . The model is two-zone (burned-unb urned) cons ideri ng the chemical kinetics of methane burni ng. The reduced burni ng mec hanism inc ludes 20 reactio ns with 15 chemical species. It was assumed that the flame, with adiabatic temperature is iu equi libri um stage. The unburned zone was considered ex tensively to ana lyze the co ndit ions that lead to knock. The ʹKnock Cri terionʹ has been used to forecas t the knock intensity. The influence of engine parameters such as spark adva nce , compression ratio aud relat ive humid ity of air intake has bee n studied on knock phenomenon. The experimental eng ine res ults from the litterature were used to validate the accuracy of our mode l. The res ults show that any increase in spark advance and compression ra tio or dec reas e in humidity of air intake will increase the probability of knock in the engine. .