针对VNT-EGR技术在国六柴油机上的应用，研究了VNT与EGR耦合对柴油机经济性和排放特性的影响规律。通过VNT与EGR开度的正交试验，并结合喷油参数进行与柴油机的优化匹配。研究结果表明：VNT增压器与EGR同时工作时，EGR开度增加导致可利用的排气能量降低，增压器的效率向低效率区域移动，减小VNT开度可改善这一现象；相同EGR开度下，减小VNT开度可以提高柴油机的空燃比，在炭烟排放水平相同的条件下，可以实现更大的EGR率，进一步降低NOx比排放，炭烟与NOx的总体排放水平有所降低，燃油消耗率随VNT开度的减小呈先降低后升高的趋势，是泵气损失与缸内燃烧状况共同作用的结果；VNT与EGR开度的正交优化大幅度降低了NOx比排放，烟度与油耗有所上升，但低速大负荷的经济性会有所改善，配合喷油参数优化，可以在满足NOx原排的条件下，经济性最优。

According to the application of VNT-EGR technology on China VI diesel engine, the influencing laws of VNT and EGR coupling on the economy and emission characteristics of diesel engine were studied. Then the optimization of diesel engine matching was conducted through the orthogonal experiment of VNT and EGR valve opening combined with the injection parameters. The results show that the efficiency of turbocharger shifts to the lower area due to the decrease of available exhaust energy caused by increasing EGR valve opening when VNT and EGR run at the same time, which can be improved by decreasing the VNT opening. Under the same EGR valve opening, reducing the VNT opening can improve the airfuel ratio of diesel engine. As for the same smoke emission level, a larger EGR rate can be achieved and the NOx emission can be further reduced. Therefore, the overall emission level of soot and NOx decreases. With the decrease of VNT opening, the brake specific fuel consumption reduces first and then increases due to the pumping loss and in-cylinder combustion. The NOx emission reduces greatly, soot and fuel consumption increase, and the economy improves at low speed and high load because of the orthogonal optimization of VNT and EGR valve opening. With the optimization of injection parameters, the economy can be optimal under the condition of meeting NOx emission target.