燃烧室形状对直喷式柴油机燃烧过程影响的仿真研究

利用CFD模拟软件Fire模拟研究了柴油机不同径深比的缩口形燃烧室对缸内混合气形成、燃烧过程和排放物形成的影响。研究结果表明:三维仿真模拟缸内压力和放热率曲线与试验值基本一致;SF5型燃烧室喷雾贯穿距长,喷雾碰壁早,燃油蒸气反弹使得喷雾分布不均匀,局部出现缺氧,炭烟排放较高;SF5型燃烧室缸内混合气混合良好,燃烧完全,缸内温度较高,NOx生成量大,可以采取推迟喷油的方式降低缸内燃烧温度,从而降低NOx排放。

Simulation Research on Influence of Combustion Chamber Shape on DI Diesel Engine Combustion Process

The influence of contracted chambers with different diameter-depth ratios on in-cylinder mixture formation,combustion process and exhaust emission formation were researched by CFD Fire software.The results indicate that the simulated in-cylinder pressure and heat release rate accord with the measured values.The penetration of SF5-shaped combustion chamber is larger and the spray impinges on the wall early.The fuel steam rebound makes the spray distribution uneven and the poor oxygen region appears,which results in higher soot emission.The mixture of SF5-shaped combustion chamber mixes well,the combustion runs more completely,in-cylinder temperature is higher,and hence more NOx generated.By delaying the injection to decrease the in-cylinder temperature,the NOx emission can be reduced.