EFFECTS OF FILM TEMPERATURE ON PISTON-RING LUBRICATION FOR REFRIGERATION COMPRESSORS CONSIDERING SURFACE-ROUGHNESS

This paper describes a theoretical model for piston-ring lubrication c onsidering the combined effects of surface roughness and oil film temp erature variation for refrigeration compressors. In the model, the pis ton-ring is treated as a one-dimensional dynamically loaded bearing wi th combined sliding and squeezing motion. The one-dimensional modified Reynolds equation, based on the average flow model by Patir and Cheng , is used to determine the pressure distribution, and one-dimensional energy equation, considering the heat generated due to contact of aspe rities, is applied to calculate the oil film temperature distribution. In the analysis of the modified Reynolds equation, the flooded condit ion and Reynolds condition are employed at the leading edge and traili ng edge of piston-ring, respectively. On the other hand, in the analys is of the modified energy equation, a constant temperature equivalent to the cylinder wall temperature is assumed at the leading edge. From numerical results of the minimum film thickness, pressure and temperat ure distributions and friction force, the combined effects of surface roughness and oil film temperature variation on the lubrication charac teristics are clarified.