不同增压型式在柴油机国Ⅵ换气系统开发中的试验研究

Experimental Investigation of Different Turbocharging Systemson Gas-exchange System Development of a Stage Ⅵ Diesel Engine

在1台满足国Ⅳ排放法规的4缸轻型柴油机上,进行了面向于满足国Ⅵ排放法规的换气系统开发的试验研究,试验分别采用废气放气阀式涡轮增压器(WGT)和可变喷嘴环涡轮增压器(VNT),配合废气再循环(EGR)阀开度的调节,研究其对柴油机性能的影响,试验结果表明:增压器压气机和涡轮机效率随EGR阀开度变化不大,VNT压气机效率与WGT基本相当,而涡轮机效率在发动机中高速工况提升明显,整体高出15%～20%;VNT在发动机中高转速工况,平均泵气压力(PMEP)和空燃比整体优于WGT,发动机换气系数改善3%～5%,燃烧热效率提升1.5%左右;在满足发动机国Ⅵ机内原始排放目标的情况下,发动机匹配VNT,经济性改善明显,较WGT综合油耗可改善2%～3%。

The experimental study of gas-exchange system development which adapts to stage Ⅵ legislation of China is carried on a stage Ⅳ lightduty 4-cylinder diesel engine. A WGT turbocharger and a VNT turbocharger are applied to the experiment respectively,and the performance of the engine is studied with the control of the open ratio of the EGR valve. Experimental results show thatthe efficiency of compressor and turbine in the turbocharger varies little with the EGR valve opening, and the compressor efficiency of VNT and WGT are basically similar while the turbo efficiency of VNT improved significantly in the medium and high engine speed condition, about 15%~20% improvement can be achieved. At the same time, VNT can get better performance of PMEP and air-fuel ratio in the medium and high engine speed condition, with the gas-exchange coefficient and combustion efficiency increased by 3%~5% and 1.5% respectively. On the condition of meeting the target of engine out raw emission of stage Ⅵ legislation of China, VNT turbocharger can get better economy efficiency and the integrated brake specific fuel consumption can be improved 2%~3% relative to WGT turbocharger.