A mixed lubrication model of textured cylinder liner-piston ring was built to investigate the effects of four array modes namely, square array, stagger array, stretching, and shortening along liner axis array of micro-dimples on the tribological properties of cylinder liner-piston ring pair. The simulation results indicate that micro-dimples can enhance the hydrodynamic effects of lube oil, improving the film bearing capability. However, the effects differ significantly under the four dimple array modes: for square array, the cylinder liner-piston ring pair is well lubricated due to the synergistic effects of uniformly spaced micro-dimples that form homogeneous bearing film even around the fired top dead center where the lubrication condition is harsh; while the film of stagger array is the thinnest among the four schemes, which means its lubrication is also the worst. From square array mode, to shortening and stretching along liner axis array, then to stagger array mode, the total friction force of cylinder liner-piston ring shows an upward trend. By utilizing laser surface texturing method, square array, stretching along liner axis array, and stagger array of micro-dimples were textured on the gasoline engine cylinder bores, followed by a set of engine bench tests. The experimental results demonstrate that the engine motored torque of the three array modes increases in turns, which validates that the anti-friction effect of square array is optimal whereas that of stagger array is the most inefficient.

Purpose The purpose of this paper is to investigate the coupling mechanism of the roughness distribution characteristic and surface textures on the cylinder liner. Design/methodology/approach The cylinder liner-piston ring lubrication model with non-Gaussian roughness distribution surface was proposed in this paper to find the optimum cylinder liner surface. The motored engine tests were carried out to verify the simulation results. Findings The calculation and experiment results show that the large negative skewness surface has the optimal lubrication performance in the un-textured liner, while in the textured liner, the small negative skewness surface is more appropriate, which means surface textures couple with small negative skewness surface can improve the lubrication performance. Originality/value Although there are some works related to liner surface roughness and textures, the combine of roughness distribution and surface textures is not usually taken into account. Therefore, this research is different from others, as the present model considers with real non-Gaussian roughness distribution liners.

Based on the characteristics of engine working conditions, the ring/liner reciprocating friction tests were conducted to research the effects of three typical cylinder liner surface topographies (honed surface, large dimple texture and small dimple texture) on the tribological performance of production piston ring pack. The experimental results demonstrated the effects of liner textures are different between three kinds of piston rings: for the barrel-shaped ringliner pair, the large or small dimple texture has its specific working condition; for the taper-faced ring-liner pair, the oil scraping efficiency and oil distributing stability can be improved by texturing small dimples on liner surface; while the dimple textures have little influence on the friction force of oil control ring-liner pair. In addition, texturing micro-dimples on liner is conducive to reducing the surface wear caused by abrasive wear, and the anti-wear effect of small dimple texture is much better.

The application of different combustion modes in engines has placed greater demands on the lubrication of cylinder liners and piston rings. In this study, a mixed lubrication model was built to investigate the tribological properties of a liner textured with micro-dimples. The simulation results indicate that surface texturing can improve the lubrication and friction properties of the ring/liner pair and adapt to different combustion modes in an engine. Due to the significant differences in external loads around top dead center of the compression stroke under pre-mixed charge combustion ignition, conventional combustion and retarded injection modes, when the liner remains untextured, the lubrication performance of the friction pair appears to be unstable in a mixed lubrication region. For the textured liner, microdimples enhance the hydrodynamic effects between the ring and liner, increasing the oil film thickness and its bearing capacity. As a result, the mixed lubrication interval shrinks and the micro asperity contact is reduced, thus improving the tribological properties of the friction pair. The numerical fluctuation ranges of parameters, the maximum asperity pressure, the average friction force and the frictional loss, are narrowed by 21.6%, 27.8% and 24.5%, respectively, under the three different combustion modes around top dead center of the compression stroke.

In this paper, a profile design of surface texture was applied for improving the tribological performance of piston ring–cylinder pair. The design of texture pattern was implemented by numerous textures of different depths in sliding speed direction to imitate the outline of barrel-shaped ring. The thickness and pressure distribution of oil film were obtained through a joint solution of modified Reynolds equation and other governing equations for textured surface. The results indicate that the novel texture pattern has the best overall performance in oil film thickness and friction force compared with normal surface textures, and the average friction power is 10.04% and 16.85% less than normal surface textures and barrel-shaped ring in the whole working cycle. Extra microhydrodynamic lubrication can be observed in the middle region of textured piston ring through the pressure distribution of oil film. At last, the experiment was conducted in a motored test rig and exhibited up to 3% reduction in friction power.