内部废气耦合点火对甲醇燃烧和排放的影响

Effect of internal exhaust gas coupling ignition on methanol combustion and emission

基于自主开发的液压可变气门机构,研究了内部废气再循环(EGR)耦合点火策略对甲醇发动机节能减排的改善潜力。结果表明,随着排气门升程的降低,内部EGR率增大。内部EGR增大导致缸内压力和缸内燃烧温度峰值下降,燃烧重心推迟,燃烧持续期延长,燃烧循环变动增加。适当地调整点火正时,甲醇发动机在42%内部EGR下仍能使燃烧重心分布在合理的范围内并平稳运行。另外,内部EGR结合点火正时在不同负荷下对油耗和排放的改善效果不同,在20%负荷下有效热效率和燃油消耗率改善效果最佳,分别提高了3.2%和12.7%;在40%负荷下对NOx和HC排放改善效果最佳,分别降低了64.25%和20.8%。

Based on the self-developed hydraulic variable valve train,the improvement potential of the internal exhaust gas recirculation(EGR)coupled ignition strategy for methanol engine energy saving and emission reduction was studied.The results show that the exhaust valve lift decreases and the internal EGR increases.An increase in internal EGR results in a decrease in the peak cylinder pressure and in-cylinder temperature,a delay in the combustion center,an increase in the combustion duration,and an increase in the variation of the combustion cycle.Properly adjusting the ignition timing,the methanol engine can still distribute the combustion center within a reasonable range and run smoothly even at 42%internal EGR.In addition,internal EGR combined with ignition timing has different effects on improving fuel consumption and emissions under different loads.The effective thermal efficiency and fuel economy are the best at 20%load,which are improved by 3.2%and 12.7%respectively.The NOx and HC emission was the best at 40%load,which decreased by 64.25%and 20.8%,respectively.