外部EGR甲醇HCCI发动机燃烧特性试验

为了控制均质压燃(HCCI)燃烧过程,在1台HCCI发动机上加装外部废气再循环(EGR)装置,进行了不同EGR率的甲醇HCCI发动机燃烧试验,采集了发动机燃烧过程的气缸压力,计算得到发动机燃烧相位、压力升高率、放热率、循环变动等参数.结果表明:外部EGR对HCCI发动机燃烧影响显著;引入部分EGR气体后,气缸最大峰值压力、压力升高率及瞬时放热率都明显降低;随着EGR率的增加,发动机燃烧相位逐渐推迟,且混合气较浓时发动机燃烧相位受EGR影响更为明显;浓混合气状态下,发动机燃烧循环变动较大,但引入少量EGR(5%)后即可迅速减小;甲醇HCCI发动机的最小燃烧循环变动量1.9%可以在中等进气浓度状态(λ=1.8)下获得.

Experimental study on combustion of methanol HCCI engine with external EGR

In order to control homogeneous charge compression ignition(HCCI) combustion,the experiments of methanol HCCI combustion with different exhaust gas recirculation(EGR) ratios are studied after adding an EGR system on the HCCI engine.The information of in-cylinder pressure is measured during the experimental process,then the combustion phase,pressure rising rate,heat release rate,and cyclical variation can be got by calculating.The results show that EGR does have some remarkable helpful influences on HCCI combustion.With the help of the external EGR gas,the peak in-cylinder pressure,pressure rising rate and instantaneous heat release rate is reduced.The combustion phase is retarded with the increase of EGR ratio,which is increased with the concentration of mixture.Under condition of rich charge mixture,the cyclical variation of HCCI combustion is obvious,but it will be reduced by introducing small amounts of EGR gas(5%).And,the lowest cyclical variation for methanol HCCI engine,1.9%,is got at the condition of middle concentration of charge mixture,λ=1.8.