Analysis of friction in surface textured components of reciprocating mechanism

Abstract

A model is presented to study the effects of inertia forces, squeeze film action and pressure boundary conditions on the friction force between a laser surface textured (LST) reciprocating components. The focus of the present paper is analysis of friction between LST piston ring and cylinder liner. The pressure distribution, the clearance and the friction force between the piston ring and the cylinder liner surfaces are obtained from a simultaneous solution of the Reynolds equation and the equation of motion. Two different approaches for analysis of the friction force are presented: “Real engine simulation” – based on a complete dynamic force equilibrium that takes into account the inertia forces and the squeeze film effects due to the piston ring mass and radial motion, respectively, while the pressure boundary conditions for the Reynolds equation represent realistic time variation in the cylinder pressure during the engine cycle; “Approximate solution” – based on a quasi-static force equilibrium that neglects inertia and squeeze film effects while applying constant ambient pressure as boundary condition. It is shown that the instantaneous friction force is much less sensitive to the real time variation of the cylinder pressure during the engine cycle than the clearance and that the approximate solution can be valid mainly for evaluating average friction values. The instantaneous clearance and friction obtained from the approximate solution may be quite different from the accurate ones.