Optimizing the tribological performance of textured piston ring-liner contact for reduced frictional losses in SI engine: Warm operating conditions

Development in surface modifications has shown promising outcomes in improving the tribological performance of contacts in hydrodynamic, mixed, and boundary lubrications. Piston ring-liner (PRL) interaction is one type of such contact. Under dynamic loading and extreme operating conditions, PRL conjunction accounts for a substantial portion of the total parasitic losses in IC engines. In this work the mixed lubrication model and realistic oil rheology are considered in order to evaluate and optimize the tribo-characteristics of partially textured barrel-shaped piston ring operating under real engine conditions. Surface texture patterns with varying shapes and orientations are considered and individually optimized to minimize energy loss. Thereafter, the performances of optimized texture patterns are compared. Optimized geometrical parameters for different rings with varying degrees of conformity with cylinder liner are also evaluated. Grooves normal to the sliding direction were found to be the top performer in the hydrodynamic regime, whereas micro-dimples perform better at piston reversals. Thus, micro-dimples resulting from the intersection of orthogonal grooves are also studied. Results show encouraging improvements in frictional behavior.