LP-EGR对增程器GDI汽油机燃烧和排放的影响

为进一步降低燃油消耗率和有害排放,开发增程器专用发动机,在一台缸内直喷(GDI)汽油机上选取增程器的3个运行工况点,开展了当量比燃烧模式下的低压废气再循环(LP-EGR)试验研究.结果表明:随着废气再循环(EGR)率的增加、点火时刻的推迟,缸内压力和放热率峰值降低且推迟,燃烧持续期延长,缸内燃烧由爆震逐渐过渡到失火,NOx排放降低.随着EGR率的增加,HC排放升高,CO和PM排放降低.点火时刻对HC、CO和颗粒物(PM)排放的影响规律随EGR率的变化而不同.引入EGR前、后的颗粒物总数量(PN)浓度值均在较低的数量级(105/cm^3).3个工况点综合优化后的最低有效燃油消耗率为219.1 g/(kW·h),较原机降低了7.75%.

Influence of LP-EGR on Combustion and Emissions of a Gasoline Direct-Injection Engine Used in Range Extender

In order to decrease fuel consumption and emissions and to develop the special engine for range extender,the effects of low pressure exhaust gas recirculation(LP-EGR)on combustion and emission characteristics were experimentally studied in a gasoline direct-injection(GDI)engine used in range extender at three operating points.The experimental results show that with increasing EGR rate and delaying ignition timing,the peak magnitude and phase of the cylinder pressure and heat release rate gradually decrease and postpone respectively.The combustion duration prolongs,combustion performances change from knocking to missing fire and NOx emissions decrease.Adding EGR rate results in the increase of HC and the decline of CO and particulate matter(PM)emissions.The influences of ignition timing on HC,CO and PM emissions depend on the EGR rate.It is also found that with or without EGR,the concentration values of total particulate number(PN)are as low as 105/cm3.After detailed optimization,the lowest brake specific fuel consumption(BSFC)of the three operation points is 219.1 g/(kW·h),7.75%lower than that of the original engine.