后喷对柴油机机油稀释的影响

Influence of post injection on oil dilution of diesel engine

利用三维仿真软件Fire建立柴油机燃烧、喷雾及机油稀释模型,分析远后喷、近后喷和喷油压力对机油稀释的影响。仿真结果表明:将1次远后喷拆分为2次,有利于降低喷雾贯穿距,减小机油稀释率;近后喷有利于提升缸内温度,加快燃油蒸发,降低机油稀释率;2次近后喷优于1次近后喷,近后喷时刻不宜超过上止点后曲轴转角60°;适当提升远后喷压力,有利于燃油雾化,降低机油稀释率。该研究可以为发动机台架标定提供参考。

The combustion,spray and oil dilution models are established by using 3D simulation software Fire to simulate the effect of late post injection,early post injection and injection pressure on oil dilution.The simulation results show that the separation of a single late post injection into double is benefit to reduce the spray penetration distance and oil dilution ratio.Early post injection can improve the temperature in cylinder,accelerate fuel evaporation and reduce oil dilution rate.Double early post injection is better than a single early post injection,and the early post injection time should not exceed 60°after TDC.The proper increase of late post injection pressure is benefit to fuel atomization and reduce oil dilution ratio.This study can provide a reference for engine bench calibration.