Modeling of Oil Transport between Piston Skirt and Cylinder Liner in Internal Combustion Engines 2019-01-0590

The distribution of lubricating oil plays a critical role in determining the friction between piston skirt and cylinder liner, which is one of the major contributors to the total frictional loss in internal combustion engines. In this work, based upon the experimental observation an existing model for the piston secondary motion and skirt lubrication was improved with a physics-based model describing the oil film separation from full film to partial film. Then the model was applied to a modern turbo-charged SI engine. The dependency of the piston-skirt FMEP on the installation clearance from the model prediction matches well the one observed from the measurements using IMEP method at the rated condition. It was found that the main period of the cycle exhibiting friction reduction is in the expansion stroke when the skirt only contacts the thrust side for all tested installation clearances. The main reason for lower skirt friction with larger clearance is greater amount of oil available during the expansion stroke.