EGR增压柴油机的燃烧及排放特性研究

Combustion and Emission Performance of Turbocharged Diesel Engine with EGR

在1台增压中冷柴油机上,采用从涡轮前取气回流到压气机后的高压EGR系统,研究了恒定转速不同负荷下发动机的燃烧和排放特性。在同一工况下,随着EGR率增加,压缩终了混合气温度升高,着火延迟期缩短,燃气压力和温度下降,燃烧持续期延长。分析了柴油机燃烧过程及排放污染物的形成机理。研究发现,当发动机负荷由大变小时,随着EGR率增加,CO的形成因受温度控制增幅越来越大,HC受着火延迟期和供氧的影响增幅越来越小,NO_x的降幅几乎随EGR率呈线性变化,而排气烟度则呈二阶多项式趋势的恶化。

On a turbocharged intercooled diesel engine,the high-pressure EGR was realized by inducing the exhaust before the turbocharger into the intake air after the compressor.At the constant speed,the combustion and emission performance at different loads were researched.At the same operating condition,the temperature of mixture at the end of compression increased, the ignition delay shortened,the pressure and temperature of burning gas decreased and the combustion duration prolonged with the increase of EGR rate.The pollutant formation and the combustion process of diesel engine were analyzed.The results show,from high load to low load,the CO emission increases due to the restraint of gas temperature,the HC emission reduces due to the influence of ignition delay and oxygen supply,the NO_x emission reduces linearly with the increase of EGR rate and the soot emission deteriorates with the second-order polynomial.