随着排放法规的升级，发动机采用闭式曲轴箱通风将成为一种趋势，但曲轴箱通风携带的油雾和PM等污染物会对发动机零部件造成污染，同时对发动机性能也会产生影响。为降低该影响，针对一台直列4缸柴油机上采用缸盖罩盖内集成预分离器，再串联一个外置分离器的两级分离曲轴箱通风方案，在发动机台架上进行了曲轴箱通风机油携带量的试验，并与开式曲轴箱通风系统进行了性能对比。结果表明：采用两级分离曲轴箱通风方案满足设计要求，可以将曲轴箱通风机油携带量控制在0.106 g/h以内，外置油气分离器分离效率在92%以上；与开式曲轴箱通风相比，闭式曲轴箱通风NRTC循环燃油消耗率仅增加了0.4%，NO_x稳态比排放基本不变，NRTC循环NO_x和PM排放分别增加了1%和3.4%，对性能标定影响不大。

With the upgrading of emission regulation, engine closed crankcase ventilation system become more and more popular, but the oil mist and PM of crankcase ventilation can contaminate engine parts and even affect engine performance. In order to reduce the effect of ventilation pollutants, a two-stage oil-gas separator system was adopted on an in-line 4-cylinder diesel engine, in which a pre-separator was integrated in the cylinder head cover and an external separator was connected in series. The oil carryover test of two-stage crankcase ventilation was conducted on an engine test bed and was compared with that of open crankcase ventilation. The results show that the twostage oilgas separator system can make the oil carryover within 0.106 g/h with above 92% separation efficiency of external separator, which can meet the design requirements. Compared with open crankcase ventilation, the BSFC, NO_x and PM emission of NRTC for closed crankcase ventilation increase 0.4%, 1% and 3.4% respectively and the steady specific NO_x emission almost keeps unchanged, which have little influence on engine performance.