EGR和过量空气系数协同控制改善甲醇发动机部分负荷性能

EGR and Lambda Coupling Controlling in Improving Part Load Performance of a Methanol Engine

通过一台柴油机改装的高压缩比(17.5)进气道喷射点燃式甲醇发动机,研究了废气再循环(EGR)和过量空气系数协同控制对甲醇发动机部分负荷经济性和排放性能的影响.结果表明:负荷越小,协同调节范围越宽,节油潜能越大,在1,400,r/min、50%,负荷时,甲醇消耗率降低幅值最大可达13.1%,,25%,负荷时甲醇消耗率最大可降低26.6%,;EGR率小于20%,或过量空气系数小于1.4时,协同控制对缸压峰值的影响较明显;当过量空气系数大于1.4后,甲醇发动机燃烧持续期急剧增加,循环变动迅速变大;与无外部EGR、过量空气系数为1相比较,合理利用EGR和过量空气系数协同控制,可以保证HC、CO排放值增幅不大且能有效降低NOx,甚至实现NOx的"零"排放.

A diesel engine with high compression ratio(17.5)was modified to a spark ignition methanol engine,and experimental study was conducted on the effect of exhaust gas recirculation(EGR)and lambda(?a)on fuel economy and emissions of engine at part loads. Results show that lower load corresponds to wider range of coupling controlling of EGR and ?a,better fuel economy. At 25%, load and 1,400,r/min,fuel consumption rate(be)reduces by 26.6%, at most,while it only decrease by 13.1%, at 50%, load. When EGR rate is less than 20%, or ?a is less than 1.4,the effect of EGR and lambda coupling controlling on peak pressure is high. When ?a is larger than 1.4,combustion duration and cycle-by-cycle variation are increased greatly. Compared with those without external EGR and ?a =1,HC and CO emissions are slightly increased,while NOx emissions are decreased remarkably,even approach zero when methanol engine uses the proper EGR and ?a coupling control.