利用文丘里管和VNT提高柴油机EGR率的研究

Study on Increasing EGR Rate of Diesel Engine with Venturi Pipe and VNT

利用文丘里管和可变喷嘴增压器(VNT)提高柴油机的EGR率,旨在降低柴油机NOx的排放。采用试验的方法研究,对文丘里管喉口直径进行了优化,分析不同的喉口直径对发动机外特性参数的影响;对于VNT系统,分析VNT叶片开度对EGR系统的影响,并在最佳的EGR率下,进行了VNT与旁通增压器的柴油机性能对比。通过文丘里管喉口直径的合理选取和VNT喷嘴环叶片位置的调节,增加涡前与文丘里管喉口的压差及EGR率。结果表明,基于VNT的EGR系统,扩展了EGR率的范围,小负荷的EGR率能达到30%,在保证柴油机动力性、经济性不变的前提下,大大地降低了NOx的排放。

Venturi pipe and Variable Nozzle Turbocharger （VNT） are used to increase diesel engine＇ s EGR rate and decrease NOx emission. The experimental study was conducted to optimize the throat diameter of Venturi pipe and investigate the effect of different throat diameters on engine full load characteristics. For VNT system, the effect of vane＇ s opening on EGR system was analyzed and engine performance with VNT and that with bypass turbocharger was compared at the optimal EGR rate. EGR rate and the pressure difference before turbine and that of Venturi pipe＇ s throat were increased by optimizing throat diameter of Venturi pipe and adjusting nozzle ring vane＇ s position of VNT. The results indicated that the range of EGR rate with VNT could be extended and reached 30% at small load. Under the condition of maintaining fuel economy and engine power, NOx emission was largely decreased in diesel engine with VNT and EGR systems.