PFI增压汽油机机油稀释试验研究

在一款1．0 L 气道喷射增压汽油机上研究了机油稀释的分布区域及其产生机理，发现机油稀释严重的区域主要集中在高速大负荷工况。通过对喷油器喷孔直径、喷油相位、VVT 动作角、空燃比、水泵流量、机油冷却器散热量、曲轴箱强制通风系统 PCV 阀补气量等相关特性参数的调整验证，发现喷油相位靠后、空燃比过浓是机油稀释严重的主要原因，水泵流量、PCV 阀补气量、VVT 动作角、机油冷却器散热量对机油稀释也有一定的影响，喷油器喷孔直径的变化对机油稀释无影响。最终在该款发动机上综合采用优化喷油相位、水泵流量、PCV 阀补气量、机油冷却器散热量的措施，最大机油稀释水平控制在5％以下。

Experimental Research on Lube Oil Dilution for PFI Supercharged Gasoline Engine

The distribution region and its mechanism of oil dilution were studied on a 1 .0 L PFI turbocharged gasoline engine . It was found that there was a serious oil dilution in high speed and heavy‐load conditions .By analyzing the influences of injection nozzle diameter ,injection timing ,VVT action angle ,air‐fuel ratio ,flow of water pump ,heat dissipation of oil cooler and flow of PCV compensating valve of positive crankcase ventilation system on oil dilution ,the lagging injection phase and the low air‐fuel ratio were thought to be the main reasons .However ,the flow of water pump ,flow of PCV valve ,VVT action angle and heat dissipation of oil cooler also had certain effect and the injector nozzle diameter had no effect .Accordingly ,the injection phase ,flow of pump ,flow of PCV valve and heat dissipation of oil cooler were optimized on the engine and the highest level of oil dilution was lower than 5% .