Boundary friction characterisation of a used cylinder liner subject to fired engine conditions and surface deposition

S.R Bewsher,M Mohammadpour,M Leighton,H Rahnejat,G Offner,O Knaus

doi:10.1016/j.triboint.2018.11.005

Abstract

In cylinder friction contributes as a primary source of parasitic dissipations in IC engines. For future engines to become more efficient, with enhanced fuel economy and increased power output, accurate prediction of new designs is required over the full lifetime of an engine. The work carried out presents use of a local pressure coefficient of boundary shear strength of asperities value, taking into account the localised effects of surface texture, coating and surface deposition. XPS spectra analysis was also carried out to identify the surface depositions as a result of combustion, not previously taken into account during piston ring pack simulation. Friction was shown by simulation to drop by up to 30% between the compression and combustion stroke as a result of using a carriable coefficient of boundary shear strength of asperities. It was found that piston varnish on the liner corresponded to higher values of the pressure coefficient of boundary shear strength of asperities, therefore showing the importance of using real system components run under representative operating conditions or numerical analyses.

Highlights

Reduction of friction and wear are key tribological objectives when designing new components and seeking new lubricant-surface combinations for Internal Combustion (IC) engines
This paper presents a unique analysis of how the deposition of combustion by-product and any resulting tribo-film in different positions along the cylinder liner affect the boundary interaction and frictional characteristics of the conjunction
The Atomic Force Microscope (AFM) measurement is carried out in order to investigate the effect of considering the real surface on the boundary friction

Summary

Introduction

Reduction of friction and wear are key tribological objectives when designing new components and seeking new lubricant-surface combinations for Internal Combustion (IC) engines. Accurate simulation plays a key role during the research and development phase of the IC engine design processes. This is of particular importance given that up to one third of the fuel energy is used to overcome friction in the engine, transmission, tyres and brakes in medium size passenger vehicles, trucks and buses [1,2]. For medium sized passenger vehicles, excluding the brake friction it is estimated that the direct frictional losses contribute as much as 28% of the total fuel energy [1]. The largest contributor to these frictional losses is the piston assembly, found to contribute on average 45% of these losses [1,2]

Methods

Results

Conclusion