【摘要】 在一台单缸直喷式柴油机上研究了废气再循环(EGR)对不同辛烷值燃料均质压燃(HCCI)发动机性能和排放特性的影响。结果表明,混合气较稀,EGR对指示热效率影响较小,其影响和燃料辛烷值有关;混合气变浓,EGR对指示热效率的影响增大。不同辛烷值燃料最高指示热效率出现在高EGR率、混合气较浓的区域,并且靠近爆震燃烧边界,辛烷值为60的燃料最高指示热效率最高,并且覆盖的工况区域最宽。高EGR率区域,EGR对HC排放的影响十分明显,EGR率升高,HC排放急剧增大,而且随着燃料辛烷值增大,这种趋势越明显;CO排放与缸内燃烧温度有较大的相关性,EGR率升高,CO排放升高。NOx排放出现急剧升高的“拐点”是判断HCCI爆震燃烧的一个重要判据,EGR率增大,“拐点”出现的混合气浓度增大,在正常工作范围内,NOx排放极低,EGR对NOx排放几乎没有影响。更多还原

【Abstract】 This paper reports the investigation of the effects of Exhaust Gas Recirculation(EGR) and octane number on engine performance and emission characteristics of homogeneous charge compression ignition(HCCI) engine.The experiment was carried out on a single-cylinder direct-injection diesel engine.The results show the highest indicated thermal efficiency of engine with different octane number appears in the area of high EGR rate and high fuel/air ratios,which is near the knocking boundary.In the region of high EGR ratio,HC emissions increases rapidly as the EGR ratio increases.With the increase of octane number,this tendency will become more obviously.CO emission has strong correlation with combustion temperature in cylinder.CO emission increases with the increase of EGR ratio.In the HCCI operation region,NO_x emission is very low and little influence from EGR on it is observed.更多还原