高低压回路EGR对柴油机燃烧过程影响的试验研究

Effects of HPL and LPL EGR on Combustion Process in Diesel Engine

在一台重型电控高压共轨柴油机上布置了高压和低压回路废气再循环(EGR)系统,并以此为基础研究了高低压回路EGR联合运行时,EGR率和高低压EGR比例对发动机缸内燃烧过程的影响,以及低负荷工况下发动机排气温度在EGR作用下的提升效果,研究结果表明:提高EGR率或增大高压EGR所占比例,都会导致进入缸内的新鲜空气量减少,最高燃烧压力下降,滞燃期延长,燃烧持续期延长;随着EGR率的提高,发动机有效热效率降低,此时需要逐渐减少高压EGR比例;引入EGR可以提升发动机低负荷工况的排气温度,但相同EGR率下,高压EGR比例越大,则排气温度提升幅度也越大。

A high pressure loop EGR（ HPL-EGR） system and a low pressure loop EGR（ LPL-EGR） system were developed on a heavy duty electronic controlled common rail diesel engine. The effects of dual-loop EGR system on combustion process in cylinder were investigated experimentally,and the study on exhaust gas temperature based on the dual-loop EGR system was also carried out. The results showed that as EGR rate or the proportion of HPL-EGR increased,the quantity of fresh air in cylinder and the peak combustion pressure decreased,the ignition delay and combustion duration became longer. As EGR rate increased,the maximum thermal efficiency decreased. To obtain a higher braked thermal efficiency the proportion of HPL-EGR should be reduced. The use of EGR could increase engine exhaust gas temperature at lowload operating points,and the more the proportion of HPL-EGR was,the higher exhaust gas temperature would become.