燃烧系统参数对商用车发动机燃烧和排放特性的影响研究

Research on the Influence of Combustion System Parameters on the Combustion and Emission Characteristics of Commercial Vehicle Engines

为改善商用车发动机性能,采用计算流体力学(computational fluid dynamics,CFD)模拟、正交设计等方法,针对某商用车的燃烧室结构参数设计了4种新方案,并选取油束夹角、喷雾锥角、主喷正时等3个喷油参数开展多因素影响研究。结果表明:燃烧室形状曲线向内收缩且最大半径增大的方案1燃烧室可提升缸内湍流特性,改善燃油浓度分布,使燃烧速度加快,油气混合更好,为最优方案。在喷油参数研究方案中,以碳烟(soot)排放为优化指标时,油束夹角对排放特性影响最大,最优匹配方案是油束夹角147°、喷雾锥角15°、主喷正时-1°,其缸内碳烟排放较原机下降13.91%,且NOx排放减少13.98%;以氮氧化物(nitrogen oxides,NOx)排放为优化指标时,主喷正时对排放特性影响最大,最优匹配方案是油束夹角160°、喷雾锥角25°、主喷正时-1°,其缸内NOx排放较原机降低37.79%。

In order to improve the performance of commercial vehicle engines,four new schemes were designed for the structural parameters of the combustion chamber of a commercial vehicle by using computational fluid dynamics(CFD)simulation,orthogonal design,and other methods.Three injection parameters,including oil beam angle,the angle of the spray cone and main spray timing,were selected to carry out a multi-factor impact study.The results show that scheme 1,where the shape curve of the combustion chamber contracts inward and the maximum radius increases,can enhance the turbulent characteristics in the cylinder,improve the distribution of fuel concentration,accelerate combustion speed,and achieve better fuel gas mixing,making it the optimal scheme.In the research of fuel injection parameters,when the soot emission is taken as the optimization index,the oil beam angle has the greatest impact on the emission characteristics.The optimal matching scheme is that the oil beam angle is 147°,the angle of the spray cone is 15°,and main spray timing is-1°.Its in-cylinder soot emissions are 13.91%lower than those of the original engine,and NOx emissions are 13.98%lower than those of the original engine.When the NOx emission is taken as the optimization index,the main spray timing has the greatest impact on the emission characteristics.The optimal matching scheme is that the oil beam angle is 160°,the angle of the spray cone is 25°,and the main spray timing is-1°.The NOx emissions in the cylinder are 37.79%lower than that of the original engine.