缸内直喷汽油机可变配气实现SICI组合燃烧方式的试验研究

An Experimental Study on SICI Combustion in Gasoline Direct Injection Engine with Variable Valve Timing

在一台装有双凸轮和可变正时机构的4缸直喷汽油机上进行了内部EGR率对理论空燃比下SICI模式的燃烧和排放影响的试验研究。结果表明,在小升程凸轮下,负气门重叠(NVO)角度在150°～50°CA范围内时,能够实现稳定的SICI燃烧。随着NVO角度的减小,内部EGR率减小,SICI燃烧的稳定范围向高负荷拓展,最佳点火角推迟。在大部分负荷范围(中小负荷),SICI燃烧模式的指示燃油消耗率明显低于传统的SI模式,在平均指示压力pmi为0.5MPa时,SICI较SI节油11%。SICI燃烧存在一个最佳的内部EGR率,NVO角度为130°～110°CA时,燃油经济性最优。另外,随着内部EGR率减小p,mi增加,NOx排放增加,THC排放减少,CO排放变化不大。

An experimental study is conducted on a four-cylinder gasoline direct injection engine with dual cam structure and variable valve timing to reveal the effects of internal EGR rate on the combustion and emission of the engine in spark ignition-compression ignition（SICI） mode at stoichiometric mixture ratio.The results show that stable SICI combustion can be achieved with negative valve overlap（NVO） in the range of 150-50°CA.With the NVO decreases,i.e.the internal EGR rate reduces,the high load range in SICI mode will extend and the optimum spark timing retard.In most of load range（medium and low loads） the fuel consumption in SICI mode is markedly lower than that in traditional SI mode.At an IMEP of 0.5MPa the fuel consumption in SICI mode reduces by 11% compared to SI mode.There exists an optimum internal EGR rate for SICI combustion： when NVO is in the range of 130-110°CA,the fuel economy reaches its best.In addition,with the reduction of internal EGR rate,IMEP increases,NOx emission rises,THC emission reduces,while CO emission has no obvious change.