Numerical Simulation Of Piston Skirt Lubrication Analysis

Piston is one of the most important parts in internal-combustion engine. Doing researches on piston hydrodynamic lubrication is significant for analyzing the piston performances of dynamics and tribology.In this paper, a mathematic model of piston skirt oil film lubrication was deduced, which based on the fluid dynamics lubrication theory and including the pressure flow factor shear flow factor contact factor. The influence of piston profile was considered. The instantaneous gas temperature and instantaneous heat transfer coefficient were calculated based on the function of engine heat working process. And the curve which described the trend of gas average heat transfer coefficient varying with the radius also could be calculated by empirical formula. The heat transference between the outer surfaces of piston and cooling water was equivalent to the heat conduction of multiple layer structure. Using the known geometric parameter, the heat transfer coefficient of the space between two individual parts of the piston outer surface could be calculated. Compiled a finite program what could show variety piston temperature and thermal deformation.The surface temperature and thermal deformation of the TBD620 engine piston skirt could be calculated by the program mentioned above. Compiled results of thermal deformation of the piston skirt into the piston skirt lubrication program in order to get the situation of hydrodynamic lubrication. And then the curves of oil film pressure and friction forces of piston skirt varying with crank angle could be gotten. The mathematic model was deduced which could describe the way cylinder vibration having an effect on oil film thickness. Using the model, the variety caused by cylinder vibration could compile in the piston skirt lubrication program to get the order how vibration works on the oil film pressure and friction forces.