EGR的热效应和稀释效应对柴油机燃烧和排放的影响

摘要

以改进的KIVA-3V程序为计算平台，在转速为1,600,r/min，每循环喷油量为52.8,mg工况下，分别进行了EGR 的热效应和稀释效应对柴油机燃烧和排放影响的数值模拟．结果表明，EGR 的热效应对滞燃期影响较大，而稀释效应成为制约最高爆发压力和缸内温度的主要因素，且随着氧气体积分数的降低，热效应对最高爆发压力的影响增强；EGR导致碳烟排放增加是由于EGR的稀释效应，低温燃烧时碳烟排放的降低是EGR的稀释效应和热效应相互作用的结果；相比稀释效应，EGR 的热效应是实现低温燃烧的主要因素，高进气热容更易改善 NOx和碳烟排放的折衷关系．%This paper presents the numerical simulation of influences of thermal and dilution effects of EGR on diesel combustion and emissions based on modified KIVA-3V source code under the speed of 1 600,r/min and the fuel injec-tion quantity of 52.8,mg per cycle of a diesel engine. The results show that the thermal effect of EGR has greater influ-ence on ignition delay,while the influence of dilution effect on in-cylinder temperature and maximum cylinder pres-sure is larger. The increase in soot emissions by introducing EGR is due to the dilution effect of EGR. Under the condi-tion of low temperature combustion,the decrease in soot emissions is due to the combined interaction of thermal and dilution effects of EGR. Compared with the dilution effect of EGR,its thermal effect is a crucial factor in realizing low temperature combustion,and high intake heat capacity is easier to improve the tradeoff relationship between NOx and soot emissions.