Effect of Coating and Low Viscosity Oils on Piston Ring Friction under Mixed Regime of Lubrication through Analytical Modelling

Anastasios Zavos

doi:10.3390/lubricants9120124

Abstract

This paper presents the impact of coating topography in piston ring-liner conjunction under mixed regime of lubrication using low viscosity oils. The study provides a time efficient analytical model including mixed-hydrodynamics regime of lubrication under different contact conditions. The method modified the expressions of the contact load and area of Greenwood-Tripp model in order to capture the real asperities interaction into contact. The model represents the tribological behavior of a thin top ring at Top Dead Centre, where boundary and mixed conditions are predominant. Electroplated CrN and PVD TiN coated rings were studied to predict the ring friction. The results are compared with an uncoated steel ring. The CrN coating shows slighter coefficient of friction, due to the coating morphology and roughness parameters. The TiN coating presents thicker lubricant films and higher coefficient of friction because the surface topography is quite rough with high peaks. This can be explained because of the major contribution of the roughness parameter and asperity slope in the boundary friction prediction.

Highlights

The ever-increasing fleet of cars, motorcycles, buses and heavy-duty vehicles leads to environmental implications due to increased CO2 emissions
An important innovation in this respect is the view of ecological tribology, which aims to minimize the environmental footprint of the Internal Combustion (IC) engine
Zavos and Nikolakopoulos [34] presented the full data of four-stroke motorbike engine, which can be used for this type of piston ring

Summary

Introduction

The ever-increasing fleet of cars, motorcycles, buses and heavy-duty vehicles leads to environmental implications due to increased CO2 emissions. High-performance engines are being downsized whilst maintaining their highest firing pressures. This trend increases the overall thermal and mechanical stresses on engine components, such as pistons, piston rings and cylinder bores [3]. Some initial studies including mixed conditions, blow-by and twist effects were conducted by Furuhama [10,11] and Tian et al [12]. Their results for rigid piston rings complied with the experimental findings using different type of engines

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Conclusion