The Finite Element Method And Its Application In Piston Skirt Lubrication

The finite element method is an efective way for numerically solving par-tial diferential equations. It was first proposed in the early1950s by engineerR.W.Clough and used to solve simple structural problems. It was in the mid-1960sthat the FEM had a mathematical basis and became a recognized mathematicsas a system of numerical methods. So far, the FEM has been widely used in thenumerical solution of most scientific and engineering fields.The piston is an important component of the internal combustion engine.It is in direct contact with high temperature and high pressure gas under highthermal load and mechanical load when the internal combustion engine is working.The main role of the piston skirt is oriented, to withstand the lateral pressure andto transfer heat. The piston skirt directly afects the formation and maintenanceof the lubricant film, the size of the piston friction. Thereby, it could determinethe mechanical efciency and lifetime of the internal combustion engine.In this dissertation the basic theory of using FEM to solve elliptic partialdiferential equation was given. Then the coupling efect between the lubricat-ing behavior and dynamic behavior of a cylinder-piston system in an internalcombustion engine was analyzed. A piston skirt lubrication numerical model inrunning conditions was established. The Runge-Kutta method was used to solvethe motion model and the FEM was applied to solve the average Reynolds Equa-tion. Oil film thickness distribution, oil film pressure and the piston swing anglewere calculated under diferent skirt profile and diferent pin ofset. Also the oilfilm friction force and friction power loss under diferent viscosity or consideringpressure-viscosity relation were presented. It shows that the noise can be reducedwhen piston pin ofset to major thrust side. Lubrication can be improved whenpiston pin ofset to second thrust side. Viscosity has a greater impact on skirtfriction losses, while the pressure-viscosity relation has less on skirt lubrication.