Fretting behavior of piston ring-cylinder liner components of a diesel engine running on TiO2 nanolubricant

Abstract

This experimental research presents the friction and wear characteristics of piston ring-cylinder liner component of a diesel engine running on commercial engine oil (5W-30) and TiO2 nanoparticle (~20 nm, ≥99.5% trace metals basis) incorporated 5W-30 engine oil (nanolubricant) to observe the performance parameters in terms of mean effective pressures and smoke emissions. Dynamic light scattering was utilized to examine the nanoparticle dispersion in the lubricant. Thermo-gravimetric analysis on nanoparticles was conducted to examine the thermal endurance during abrasion tests. The samples directly cut from the spare piston ring of the test engine underwent severe friction and wear tests via linear friction module. Coefficient of friction was considered as comparison param-eter to understand the tribological behavior of friction pairs submerged in two different lubricants. Scanning electron microscopy analysis was conducted to observe morphology of the nanoparticle and to analyze the surface structure of the samples before and after the abrasion tests. Atomic force microscopy analysis was done to obtain the 3D images of the worn surfaces and to make a comprehensive comparison of tribological performance between engine lubricant and nanolubricant. The results depicted that, TiO2 is effective in reducing coefficient of friction by an average of 10.37% and wear rate by 33.58% as well as improving brake mean effective pressure by an average of 4.95% and reducing friction mean effective pressure by an average of 9.34% when compared to those of the engine oil. In parallel with reduced friction, TiO2 incorporation in engine oil yielded an average reduction of 9.11% in smoke opacity. The experiments suggest promising results in terms of utilization of low friction, fuel efficient and environmental friendly internal combustion engines fulfilling strict emission regulations.