Three-Dimensional Analysis of Tribological Performance and Heat Transfer in Piston and Cylinder Liner System

摘要

A three-dimensional, hydrodynamic mixed lubrication model has been developed to investigate the frictional performance of piston ring and cylinder liner contact. The model is based on the average Reynolds equation and asperity contact approach with the considerations of surface roughness, rupture location, blowby through the piston ring pack and nonaxisymmetry in circumferential direction of cylinder liner. The equation has been solved cyclically using the finite difference method in a fully flooded inlet boundary condition and a flow-continuity Reynolds boundary condition for cavitation outlet zone. The oil film thickness, hydrodynamic pressure distribution, friction force and friction heat generated at the piston ring/cylinder liner interface are determined as the function of crank angle position. The results show that the shape of the cylinder liner (out-of-roundness) significantly affects the lubrication performance of the piston ring pack. A heat transfer model has been presented to evaluate the effects of friction heat on the temperatures of piston and cylinder liner system. The friction heat is added on the piston ring/cylinder liner interface as the flux boundary condition. The temperature fields of piston and cylinder liner system are acquired by the FEM, which reveal the distribution of the friction heat in this system. The results show that the friction heat mainly affects the temperature on the region near the top ring groove of the piston ring pack. The effect decreases at the region away from the top ring groove, especially at the piston skirt. The effect of friction heat on the temperature of cylinder liner is smaller than that of piston ring pack.