Friction at Ring-Liner Interface Analyzed with a Systematic Surface Characterization

The ring-liner interface of an internal combustion engine is a very important interface because its behavior directly affects fuel efficiency of an automobile and the engine life. The liner surface is complicated, with honing features on top of the primary roughness. Moreover, liner surfaces considered here also contain pores that are random in terms of their shape and distribution. The work reported in this article systematically models the tribological performance of such surfaces in a ring-liner interface. A microscopic single-pore computational fluid dynamics analysis is conducted on the representative pore shape obtained from liner-surface characterization to quantify the effect of pores on friction. A pore influence zone is suggested, and a friction reduction factor is defined for pores. A macroscopic ring-liner interface model is developed in parallel to solve the average Reynolds equation for a representative section with the consideration of the starvation and cavitation effects. The two models are then combined to predict friction at the ring-liner interface for the liner surfaces with pores. Excellent agreement is observed between our modeling and experimental results. The effects of random pores of varying densities in the range of 2-10% on the ring-liner interface performance are studied under flooded and starved conditions. The results indicate that surface pores increase friction when the ring-liner set is operated under flooded conditions. However, when starvation occurs, surface pores help reduce friction.