柴油机米勒循环结合EGR的性能分析及优化

Performance Analysis and Optimization of Miller Cycle Combined with EGR

文章建立了增压柴油机米勒循环结合EGR(废气再循环)的热力学模型,利用模型分析了柴油机设计参数对其性能的影响,为米勒循环结合EGR的增压柴油机参数设计提供了理论依据。研究表明,要使WP7柴油机的热效率和平均有效压力同时提高,增压系统效率需大于0.7。同时,以柴油机转速为1 500 r/min外特性工况点的NO_X排放下降50%、最高爆发压力不超过原机为约束条件,对WP7柴油机参数进行了优化设计。优化结果表明,该方法将有效压缩比从18降低到15.5,再结合12%的EGR率,可以在保持柴油机经济性、动力性与原机基本一致的前提下,将NO_X排放下降50%以上。

A thermodynamic model of turbocharged diesel engines is developed for Miller cycle combined with EGR. The influence of design parameters on the diesel engine performances is analyzed based on the model, which provides a theoretical basis for Miller cycle combined with EGR diesel engines. The research shows that the efficiency of turbo-charging system must be more than 0.7 in order to improve the thermal efficiency and mean effective pressure of WP7 diesel engine at the same time. The WP7 diesel engine design parameters are optimized in the constraint conditions of NOX emission decreasing 50% and the maximum cylinder pressure no more than the original engine in full load of 1 500 r/min. The optimization results show that reducing the effective compression ratio from 18 to 15.5 and using 12% EGR ratio make the NOX emission decrease more than 50%, while the economy and power performances are consistent with the original engine.