基于EGR技术的国Ⅳ重型柴油机燃烧系统开发

Development of a Stage Ⅳ Heavy-Duty Diesel Engine Combustion System Based on EGR

在一台电控重型柴油机上进行了基于EGR技术的燃烧系统开发研究,组建了基于WGT增压器的电控高压EGR系统,研究了燃烧室、喷油器、增压器、EGR率及喷油参数等对柴油机性能和排放的影响,确定了最终的重型柴油机国IV燃烧系统优化方案.结果表明:通过优化匹配燃烧室和增压器并采用孔径较小的多孔喷油器能显著改善柴油机NOx和烟度之间的折衷关系;小负荷时,推迟喷油可以使NOx在降低较多的情况下烟度略有下降;随着EGR率增加,提高喷油压力与推迟喷油相结合,可以同时降低大负荷的NOx和烟度排放,并能改善燃油经济性.ESC循环测试结果表明,通过对燃烧系统、EGR和喷油控制参数的综合优化,在不采用后处理器的情况下,柴油机各气体排放(NOx、HC和CO)及微粒(PM)均达到国Ⅳ排放标准,十三工况加权油耗率与原机基本相当.

Development of combustion system based on EGR was made on an electronically controlled heavy-duty diesel engine. An electronically controlled EGR system based on WGT turbocharger was established. Effects of combustion chamber, injectors, turbocharger and EGR ratio on diesel engine performance and emission were studied. The optimal national stage IV combustion system was determined. Results show that, by optimally matching combustion chamber and turbocharger and using smaller multi-aperture injectors, the NOx-PM trade-off can be apparently improved. At small load, NOx can be reduced obvi- ously with retarded injection timings whilst PM reduces slightly. When EGR ratio is increased, the emissions of NOx and PM can be simultaneously reduced with increasing injection pressure and retarding injection timings. Fuel economy can be improved at high load. ESC cycle test results show that through integrated optimization of combustion chamber, EGR and injection parameters, gas emissions （NOx, HC and CO） and particulate matter （PM） can meet national stage IV Emission Regulation and weighted specific fuel consumption is almost same when compared with that of original engine without exhaust aftertreatment systems.