Analysis of lubrication and friction for a complete piston-ring pack with an improved oil availability model: Part 1: Circumferentially uniform film

Abstract

The study of the tribological performance of piston rings plays an important role in piston assembly design. In this study, a comprehensive analysis of piston-ring pack lubrication has been developed. The model employs a flow-continuity algorithm and considers relative ring locations in the piston-ring pack as well as oil accumulation in front of the ring in determining the oil availability. The computer model is able to predict the effect that bore distortion and ring conformability have on piston-ring performance. (This influence is discussed in Part 2 of the paper). In this part of the paper (Part 1), the theoretical formulation of the model is briefly described. The model is verified through comparison of the calculated ring-liner film thicknesses with those measured experimentally by Hamilton and Moore on a diesel engine. Then some results, obtained under situations where film thicknesses are circumferentially uniform, are presented to simulate a piston-ring pack in a modern petrol engine as an example to demonstrate the capabilities of the model and to show the effects of some important factors on the performance characteristics of the ring pack. The authors have found that the model developed is a robust one which can be used to analyse the tribological performance of ring packs effectively in both circular and distorted cylinder bores of internal combustion (IC) engines.