可调二级增压结合EGR策略对米勒循环柴油机性能的影响

针对米勒循环柴油机新鲜充量系数低,扭矩输出能力不足的问题,引入了电子增压器(E-Booster)技术,讨论可调二级增压结合EGR策略对米勒循环柴油机性能的影响。在1400r/min,pme=1.85MPa工况分析了米勒度、二级增压策略以及EGR对柴油机性能及NOx排放的影响。仿真结果表明:无论是在进气门早关还是进气门晚关策略下,随着米勒循环的加深,缸内燃烧温度逐渐下降,使得NOx排放降低,但由于循环充量系数的减少,扭矩输出降低;采用E-Booster可调二级增压方案,合理控制E-Booster的介入策略,提高进气压力,能够弥补米勒循环扭矩输出能力的不足,同时提高燃油经济性,但也会造成缸内最大压力和NOx排放的增加;采用EGR策略则能够弥补由较高进气压力造成的不利影响,降低机械负荷和NOx排放。米勒度、pin、πH、EGR率分别为M30、0.286MPa、7%、10%时,pme,ac提高0.03MPa,同时NOx排放下降0.47g/(kW·h),有效改善了米勒循环柴油机动力性和NOx排放。

Effects of Adjustable Two-Stage Supercharging and EGR Strategy on Performance of Miller Cycle Diesel Engine

Due to the low fresh charge and insufficient torque output of Miller cycle Diesel engine,the effects of adjustable two-stage supercharging and EGR strategy on the performance of Miller cycle diesel engine were discussed after the introduction of e-booster technology.The effects of Miller degree,two-stage supercharging strategy and EGR on diesel engine performance and NOx emission at 1 400 r/min with BMEP of 1.85 MPa were analyzed.The results show that the in-cylinder combustion temperature gradually decreases with the reduction of NOx emission and the torque output also reduces due to the reduction of charge with the deepgoing Miller cycle under early intake valve closing (EIVC) or late intake valve closing (LIVC) strategy.Controlling the e-booster properly to increase the intake pressure can compensate for the shortage of Miller cycle torque output and improve fuel economy,but it can also lead to the increase of maximum pressure and NOx emission.EGR can avoid the side effects caused by higher intake pressure and reduce the mechanical load and NOx emission of diesel engine.BMEP AC increases by 0.03 MPa and NOx emission reduces by 0.47 g/(kW·h) when Miller degree,p in,π H and EGR is M30,0.286 MPa,7% and 10% respectively,which improves the combustion and NOx emission of diesel engine effectively.