新型EGR系统对非道路柴油机性能和排放的影响

Study on the Effects of a New EGR System on Performance and Emission of Non-Road Diesel Engine

结合非道路柴油机,设计了一种简单、低成本的废气再循环(EGR)系统,采用八工况法实验研究了该EGR系统对非道路用柴油机燃油经济性和排放特性的影响。研究结果表明:该系统EGR率主要受涡前排气压力与进气增压压力差的影响,两者的正压差越大,EGR率越大;在八工况测试中获得的最大EGR率约为12%;在高负荷工况,EGR对柴油机的燃油经济性影响不明显;但在中等负荷工况,随EGR率增大,经济性略有恶化;在低负荷工况,由于过量空气系数较大,EGR率的影响较小;引入非冷却EGR后,各工况的NO_x和HC排放均有不同程度的降低,但烟度排放有不同程度的增加。非道路柴油机采用该EGR系统的八工况加权比排放量满足第三阶段排放限值的要求。

Combined with a diesel engine, a simple and low-cost exhaust gas recirculation（EGR） system was designed. The effects of the EGR system on the fuel economy and emission characteristics of non-road diesel engine were experimentally studied by adopting eight-mode test cycle. The results show that the EGR rate of the system is mainly affected by the pressure difference between the exhaust pressure before turbine and the intake boost pressure. And the larger the pressure difference, the larger the EGR rate is.The maximum available EGR rate is about 12 percent in the eight-mode test cycle. The effect of EGR on fuel economy of the diesel is not obvious at high-load condition, but the economy is deteriorated with increased EGR rate at medium-load condition. At low-load condition, moreover, the effect of EGR is weak due to large lambda. After the non-cooled EGR is introduced, the NOx and HC emissions of each condition are reduced to different degrees, but there is a certain increase in smoke emissions. In this study, the weighted specific emissions of eight-mode test cycle for the non-road diesel engine can meet the emission limits of China Ⅲ by adopting the EGR system.