Prediction of oil behavior in piston ring groove based on gas-liquid two-phase flow analysis

摘要

In recent years, many vehicles with internal combustion engines use low tension piston rings and low viscosity oils to reduce friction loss around the rings. However, the reduction of ring tension causes problems in oil consumption. We conducted the prediction of oil behavior around the oil control ring by two-phase flow simulation based on the level set method towards revealing the mechanism of several problems around the piston ring that included oil consumption. Firstly, the calculation results of the dam break, a benchmark problem for two-phase flow analysis, showed the validity of the analysis code. Then, we calculated the flow field around the ring and compared with experimental values at each grid resolution. The calculated values showed the same tendency as the experimental values in the case where the computational grid is enough for the oil film. Besides, the oil behavior is not only dominated by using the inertial force, but also by the vortex formed due to cylinder pressure. The calculation also suggested that the amount of oil in the groove affected transportation leading to oil consumption. From the investigation of the effect of oil viscosity, the thick part of the oil film was affected by the inertial force of the piston, and the thin part was affected by the viscosity. Moreover, the effect of the surface tension also affected the behavior of the oil under certain conditions. The result that assumed low viscosity oil showed the behavior that leads to oil transport.