涡流比对NOx与Soot排放影响的数值模拟

Numerical Simulation of the Swirl Ratio on NO_x and Soot

影响直喷式柴油机缸内燃烧过程和排放特性的因素可归纳为3个方面,即进气系统参数、喷油系统参数以及燃烧系统参数。基于某企业开发的6缸直喷式柴油机,以AVL公司的FIRE v8.5为平台,以进气系统参数具有代表性的物理参数涡流比为对象,研究了它对直喷式柴油机排放性能的影响规律。在涡流比从1.0增加到2.6的过程中,随着涡流比的增大,喷雾重叠加剧,并向燃烧室挤流区域集中,燃烧室凹坑内空气利用率变差,不利于柴油机的扩散燃烧,Soot排放增大;在涡流比增大的同时,降低了整个燃烧室的平均温度,使NOx的生成量降低。

The factors Affecting cylinder direct injection diesel engine combustion process and emission characteristics can be summarized into three areas: intake system parameters,parameters of fuel injection system and combustion system parameters.Based on a cylinder direct injection diesel engine of 6 to AVL's FIRE v8.5 as a platform,one physical para meters,which was swirl ratio representatively to study their influence on cylinder direct injection diesel engine combustion and emission properties.When the swirl ratio varies from 1.0 to 2.6,as the swirl ratio increases,spray overlap was increased and the spray was concentrated to the combustion chamber squish region,resulting in the deterioration of air utilization rate in the combustion chamber pit,which is not conducive to the spread of diesel engine combustion,then Soot emissions increase.At the mean while,the average temperature of the combustion chamber was down due to the increase of swirl ratio,which reduced the amount of NOx generation.