EGR率对阿特金森发动机稀薄燃烧及排放的影响

Effect of EGR rates on combustion and emissions of an Atkinson engine in lean burn

基于1台1.5 L直列三缸缸内直喷汽油机,开展不同EGR率下的过量空气系数(λ)扫描试验,探究不同程度的稀薄燃烧工况下EGR率对燃烧和排放的影响。研究结果表明:EGR率和λ增大均会导致峰值压力下降,燃烧循环变动率增大,燃烧推后并且持续期延长。指示燃油消耗率随EGR率增加而增加,随λ增加先升高后降低。当EGR率为0、λ为1.15时,燃油消耗率出现最小值。引入EGR可大幅降低NO_(x)排放,但会导致HC排放增多,通过一定程度的稀薄燃烧可以抑制HC上升。同时,稀薄燃烧对降低CO排放的效果也明显比EGR的效果大;当EGR率为0时,通过稀薄燃烧可使CO排放最大下降86.7%。因此,稀薄燃烧与适量EGR率(7%)耦合可作为降低发动机综合排放的一个有效手段。

Based on a 1.5 L three-cylinder direct injection gasoline engine,the bench test was set up,and excess air coefficient(λ)was scanned with different EGR rates to investigate the effects of EGR rates on combustion and emissions at different degrees of lean burn.The results show that the increase of EGR rate andλleads to the decrease of peak pressure,the increase of combustion cycle variation rate,and the obvious lag and prolongation of combustion period.The indicated fuel consumption rate increases with the growth of EGR rate,and increases first and then decreases with the increase ofλ.When the EGR rate is 0 andλ=1.15,the fuel consumption reaches a minimum.The introduction of EGR can significantly reduce NO_(x)emissions but will lead to an increase in HC emissions.The rise of HC can be inhibited by a certain degree of lean combustion.Meanwhile,the reduction effect of lean burn on CO emission is also significantly greater than that of EGR,and the maximum reduction of CO is 86.7%at the EGR rate of 0.Therefore,lean-burn coupled with appropriate EGR(7%)can be used as an effective means to reduce the comprehensive emission.