气道喷水和废气再循环对重型柴油机性能和排放影响的优化匹配试验研究

在一台高压共轨重型柴油机上开展了气道喷水结合高压废气再循环(EGR)的试验研究。基于世界统一稳态测试循环(WHSC)各工况点探索引入高压EGR和气道喷水技术对柴油机排放和燃油经济性的影响;在此基础上对各工况的燃烧相位进行优化,得到WHSC各工况点下基于喷水和EGR的优化策略。结果表明:综合考虑排放和燃油经济性,低负荷工况宜单独引入高压EGR,并通过提前喷油时刻(start injection timing,SOI)优化燃烧相位;中高负荷工况宜少量喷水并引入适当EGR,满负荷则应单独采取气道喷水策略。WHSC加权结果表明,在保持较低的HC、CO和碳烟排放前提下,优化后的加权NOx比排放降低7.71g/(kW·h),降幅约45.2%,有效燃油消耗率降低约1.20g/(kW·h)。

Experimental Study on Effects of Inlet Water Injection and Exhaust Gas Recirculation on Performance and Emissions of a Heavy-Duty Diesel Engine and Corresponding Optimization Strategy

An experimental study of inlet water injection combined with high pressure(HP) exhaust gas recirculation(EGR) was conducted on a high pressure common rail heavy-duty diesel engine. The effects of introducing HP EGR and inlet water injection on diesel engine emissions and fuel economy were investigated at all working points of the world harmonized steady-state cycle(WHSC). Based on that, the optimization of the combustion phase at each working point was carried out to obtain an optimal control strategy of coupling inlet water injection with EGR over the WHSC cycle. The results show that, considering both the emissions and fuel economy, the HP-EGR should be introduced at low load conditions and the fuel injection timing should be advanced to obtain a better combustion phase. A small amount of inlet water injection and a proper rate of EGR should be adopted at medium and high load conditions, while the inlet water injection strategy should be adopted at full load. The weighted WHSC results show that the optimized weighted NOx specific emissions can be reduced by 7.71 g/(kW·h), a reduction of about 45.2%, and the weighted brake specific fuel consumption(BSFC) can be decreased by 1.20 g/(kW·h), while still maintaining low HC, CO and soot emissions.