米勒增压直喷汽油机应用LPEGR的试验研究

An Experimental Study on LPEGR Application in a Miller Turbocharged Direct-Injection Gasoline Engine

对一台应用LPEGR的米勒增压直喷汽油机进行了试验研究,分别阐述了LPEGR对小、中、大负荷的油耗和排放的影响。小负荷时引入LPEGR,节油效果不理想;中负荷时,在燃烧稳定性方面可以容忍较高的EGR率,2000 r/min@1.2 MPa时应用22%EGR,可以节油5.6%;大负荷时,COVIMEP对EGR比较敏感,2000 r/min@1.4 MPa时应用15%EGR,可以节油3%。EGR可以降低中大负荷的NOx排放,但会增加THC排放。介绍了进气节流阀的效果,在低转速中小负荷区域,可节油约1%。对比了不同漏气量的2种节流阀优化EGR阀压比的效果,保持相同的EGR阀和节油阀开度,即使采用小漏气量节流阀,EGR阀压比也较难降低;若保持相同的EGR率,采用小漏气量节流阀,EGR阀压比降低幅度较大,有利于提高EGR模型控制算法的鲁棒性。

In this paper,LPEGR is applied to a Miller turbocharged direct-injection gasoline engine.Firstly,the influence of LPEGR on fuel consumption and emission is expounded respectively.Medium load can tolerate higher EGR rate in combustion stability.22%EGR at 2000 rpm@12 bar can save 5.6%fuel.COVIMEP of large load is sensitive to EGR.15%EGR at 2000 rpm@14 bar can achieve 3%fuel saving.LPEGR can reduce NOxemissions but increase THC emissions.Then the effect of intake throttle valve is introduced,which can save about 1%fuel in low speed and low-mid load area.Finally,the optimization effect to EGR valve pressure ratio is compared between two intake throttle valves with different air leakage.When the same valve opening is maintained,EGR valve pressure ratio is difficult to pull down even if adopting little air leakage throttle valve.If EGR rate is kept the same,EGR valve pressure ratio will be significantly reduced with little air leakage throttle valve,which is conducive to improve the robustness of EGR model control algorithm.