Experimental Research on EGR in a Diesel Engine Equipped with Common Rail Injection System

Emission control is a focus of Diesel technology development all over the world. EGR is considered as a most efficient method to reduce the NOx exhausted and there has also been published a significant amount of studies on EGR. As one part of evaluation of engine technologies of PNGV plan, this research tried to investigate comprehensively what effects cooled and hot EGR imposes on exhaust emissions in a developing light duty high-speed direct injection (HSDI) Diesel engine equipped with high-pressure common rail (HPCR) multiple-stage injection system, VNT and cooled/hot EGR. The test is carried out on a 3-cylinder CR engine. In the condition of the other control parameters being optimized, EGR map is adjusted for different EGR rate. Then, the effect of EGR on emissions is investigated under different EGR rates. The experimental tests showed that, Exhausted NOx emission declined about 73 to 88 percent in tested EGR range, and some benefit is found on HC and CO at the same time, as well as PM kept almost unchanged with lower EGR rate at lower engine load and trended increase with larger EGR. Moreover, the test results at lower engine load with larger A/F ratio test condition indicated that, in such case, engine-working temperature would take a remarkable effect on HC emission.