Solution of the Lubrication Problem and Calculation of the Friction Force on the Piston Rings

Abstract

The Finite Element (FEM) is applied to solve the governing equations of lubrication of the piston rings and to calculate the friction force on each ring. The ring is assumed to have a circular profile in the direction of motion. This profile changes with time because tilting of the ring with the engine cycle is taken into account. In the circumferential direction, the ring is assumed to be a perfect circle and the bore cross-section is assumed elliptic. Mixed lubrication is considered when the oil film thickness becomes smaller than a certain value which depends upon the roughness of the surfaces in contact. The friction coefficient for this lubrication is taken as a function of the oil film thickness and the surface roughness. The predictions of the friction force are compared with experimental friction data for the same engine.