稀燃和EGR对汽油发动机性能影响研究

基于一台带有低压废气再循环系统的1.5 L涡轮增压直喷汽油发动机进行了稀燃和废气再循环(EGR)影响发动机燃烧性能的试验研究。结果表明,随着稀释率的上升,EGR和稀燃均导致发动机滞燃期、燃烧持续期延长,燃烧重心提前,有效燃油消耗率下降,排气温度下降,平均绝热指数上升。相同稀释率下,相比稀燃,EGR的滞燃期长,燃烧重心提前,两者燃烧持续期基本相等,稀释极限低,绝热指数小,排气温度低。在稀释率分别为20%、35.9%时,最大可减小有效燃油消耗率4.7%、7.2%。热容对燃油经济性的影响占主导地位,相同稀释率下,循环变动系数小于3%时,相比稀燃,EGR具有更好的燃油经济性。

Effect of lean combustion and exhaust gas recirculation on the performance of gasoline engine

Effect of lean combustion and exhaust gas recirculation (EGR) on the combustion performance of a 1.5 L turbocharged gasoline direct injection engine with low pressure exhaust gas recirculation system was studied. The results showed that with the increase of dilution rate, both EGR and lean combustion led to the prolonged ignition delay and the combustion duration, the advanced combustion center, the decreased effective fuel consumption rate, the decreased exhaust gas temperature, and thus the increased average adiabatic index. At the same dilution rate, compared with lean combustion, EGR caused longer ignition delay, earlier combustion center, basically identical combustion duration, lower dilution limit, smaller adiabatic index, and lower exhaust temperature. When the dilution rates were 20% and 35.9%, the maximum effective fuel consumption could be reduced by 4.7% and 7.2% via EGR and lean combustion, respectively. Heat capacity played a dominant role in the fuel economy. EGR has better fuel economy at the same dilution rate when cyclic variation was lower than 3%.