EGR阀升程规律对重型柴油机瞬态工况排放特性的影响

Effects of EGR Valve Lift Law on Emission Characteristics of Heavy Duty Diesel Engine under Transient Conditions

基于1台配备废气再循环系统(EGR)的重型柴油机,试验研究了瞬态工况下EGR阀升程规律对重型柴油机排放特性的影响。针对恒转速变扭矩与恒扭矩变转速过渡工况设计了5种EGR阀升程规律,根据升程走势可分为3种类型:线性升程,上凸型升程以及下凹型升程。结果表明:瞬变过程中,初始EGR阀开度变化速率对NO_x生成影响巨大,NO与NO_x排放规律基本吻合,EGR阀升程规律对NO_2排放影响甚微。不同EGR阀升程规律下烟度变化规律相同,呈先增后减的趋势,但峰值明显不同。EGR阀升程规律对燃油经济性影响不大。

The effects of different EGR valve lift laws on emission characteristics were studied under transient conditions on a heavy duty diesel engine equipped with the exhaust gas recirculation system(EGR).Five kinds of EGR valve lift laws were designed according to the transition conditions of constant speed and changing torque and that of constant torque and changing speed,which could be categorized into three types such as linear transition,convex transition and concave transition.The results show that the change rate of initial EGR valve opening has a great impact on NO x formation during the transient process.The changing trend of NO emission is the same as that of NO x emission.In addition,the lift laws of EGR valve have little effect on NO 2 emission and fuel economy.The soot emission has the same changing trend with the characteristics of first increase and then decrease under different lift laws of EGR valve,but peak values vary obviously.