희박성층연소조건의 분무유도식 DISI 엔진에서 LPG연료의 연소 특성

In this study, a single cylinder engine experiment under lean stratified conditions was carried out to investigate combustion and emission characteristics of a spray guided direct injection spark ignition engine fueled with gasoline and LPG. In the result of the engine experiment, the flammable window limited by misfire in the case of LPG was narrower than that of gasoline. IMEP in case of LPG was higher where no misfire occurred even though the maximum heat release rate was lower. This was because that combustion phase was retarded, leading to reduced negative work and low in-cylinder temperature during combustion. HC emissions referring the combustion efficiency were higher while NOx and smoke emissions were lower than those of gasoline. In the result of the a experiment to visualize the mixture formation, the spray penetration of LPG was just enough to be ignitable where no misfire occurred and was shorter than that of gasoline. The penetration of spray became shorter as injection timing was retarded, which was the reason of misfire leading the narrower window. This result is likely be due to the high evaporating characteristic of LPG fuel.