EGR对涡轮增压柴油机瞬态特性的影响

摘要

Experiments of load increasing at constant speed and speed increasing at constant load were conducted on a turbocharged diesel engine with EGR (exhaust gas recirculation).The changing trends of operation parameters of diesel engine versus EGR valve opening was analyzed.Results show that,for the load increasing at constant speed,because of response lag of the turbocharger and mutual influence of inlet and outlet gases,air fuel ratio is decreased and soot emission is increased.For the transient acceleration,the intake flow lag phenomenon is unobvious,air fuel ratio is decreased and soot emission is increased.In the whole transient experiment,intake oxygen volume fraction has greater influence on NOx emission than EGR rate.Because of the change of the intake gas state,the traditional EGR control method based on EGR rate is unsuitable for the transient operating conditions of diesel engine.%通过一台电控单体泵柴油机进行定转速瞬态加载和定负荷瞬态加速试验,分析不同废气再循环(EGR)阀开度下柴油机重要性能参数在瞬态工况时的变化趋势.结果表明:在瞬态加载过程中,由于增压器响应滞后以及进/排气的相互影响,进气滞后现象严重,空燃比下降且碳烟(soot)排放值升高;在瞬态加速过程中,进气流量滞后现象不明显,由于油量超调引起过量空气系数减小,使得soot排放量增多;在整个瞬态试验过程中,氮氧化物(NOx)排放变化趋势与进气氧体积分数变化趋势的相关程度高于EGR率.在瞬态工况下,由于进气状态发生变化,传统的基于EGR率的EGR控制方法已不适用,需要研究新的柴油机瞬态控制策略.