Elastohydrodynamic Piston Skirt Lubrication: Effect on Tribological Performances

Abstract

A model of elastohydrodynamic lubrication of piston skirt is developed in this paper. The secondary motion of the piston, the lubrication and the elastic deformations of skirt and cylinder are described by a transient strongly nonlinear system coming from the coupling of the dynamics equations of piston secondary motion and the Reynolds equation. The iterative Newton-Raphson method in conjunction with Murty’s algorithm for cavitation was used to solve the problem. An optimum skirt curved profile, which maintain piston in optimum performance characteristics, is adopted. Using the tribological performance of the lubricated skirt-cylinder, the results — minimum oil-film thickness, maximum pressure in the lubricant film and friction — are compared to the elastohydrodynamic solution and the rigid skirt-cylinder solution. The effect of elastic deformation of both skirt and cylinder show that elastohydrodynamic analysis is necessary for an accurate prediction of a piston-cylinder performance. The computational work, applied to a solid skirt piston of a V-8 direct injection diesel engine truck, should be a powerful design analysis tool, which can be used to increase the available engine power through optimum piston performance characteristics.