EGR对甲醇HCCI发动机燃烧与排放的影响

针对均质压燃燃烧难以控制的问题,在一台发动机上,改装进排气系统,并加装均质混合气供油系统和进气加热系统,研究了外部EGR（废气再循环）对甲醇HCCI（均质充量压缩着火）燃烧与排放特性的影响。结果表明：外部EGR对甲醇HCCI燃烧过程和排放都有显著的影响,随EGR率的增加,CA10、CA50逐渐推迟,燃烧持续期逐渐延长,但影响的程度因混合气浓度的不同而变化;HC和CO排放逐渐增加,且增加的幅度逐渐变大;NOx排放仅在混合气较浓时存在（过量空气系数小于1.5时）,且随着EGR率的增加迅速下降。

Effect of EGR on combustion and emission of methanol HCCI engine

In order to deal with the problem that the combustion of homogeneous charge compression ignition(HCCI) is difficult to control,the impacts of external exhaust gas recirculation(EGR) on methanol HCCI combustion and emission characteristics were investigated on a modified engine by modifying intake and exhaust system,adding HCCI fuel supply system and intake-heating system.The results show that the EGR has a remarkable influence on the combustion and emission of methanol HCCI.As the EGR ratio increases,CA10 and CA50 gradually delay and the combustion duration prolongs,the change level varies with the differences of mixture concentration,the emissions of unburned hydrocarbon and monoxide carbon quickly increase.Nitrogen oxide can only be detected at the condition of relative richer mixture(air-fuel equivalence ratio less than 1.5),and its quantity decreases quickly with the EGR ratio going up.