Research on Tribological Performance of Cylinder Liner by Micro-Laser Surface Texturing

Improvement of tribological performance and minimization of frictional losses is important for the friction pairs like cylinder liner-piston ring pair. Laser Surface Texturing (LST) technique was employed to improve the tribological performance by producing the micro-dimples on the cylinder liner surface in a light-duty diesel engine. An analytical mixed lubrication model of cylinder liner-piston ring was developed considering the surface roughness and the synergistic effect of multi micro-dimples, which was solved by modified multi-grid method, to simulate its tribological performance. The simulation results show that compared to lubrication model with ideal smooth surface, the presented model can most truly reflect the engine's tribological behavior in working cycle such as oil film thickness, oil film pressure, asperity contact pressure, and dimensionless friction force. Near the Top Dead Center (TDC) and the Below Dead Center (BDC) areas, the friction pair is under the mixed lubrication state, and the asperity contact plays a dominant role in balancing external load and the peak friction force appears. However, micro-dimples formed by LST can still bring some appropriate hydrodynamic lubrication effect. At the other areas except TDC and BDC, hydrodynamic lubrication effect is more obvious. It shows that the formed micro-dimples through micro-LST in the cylinder liner surface can make pronounced improvement in the lubrication behavior of cylinder liner-piston ring. The investigation results also show that the cylinder liner surface roughness has a great influence on the lubrication performances. The minimum oil ratio increases with the decreasing surface roughness of the cylinder liner, while the dimensionless friction force and friction power decrease. As the surface roughness changes from 0.6 mu m to 0.2 mu m, the minimum oil ratio of the central part of the engine strokes is doubled, while the dimensionless friction force and friction power loss reduce by 50% at the vicinity of TDC.