Modeling and Optimizing Honing Texture for Reduced Friction in Internal Combustion Engines 2006-01-0647

Frictional losses in the piston ring-pack of an engine account for approximately half of the total frictional losses within the power cylinder of an engine. Three-dimensional honing groove texture was modeled, and its effect on piston ring-pack friction and engine brake thermal efficiency was investigated. Adverse effects on engine oil consumption and durability were also considered.

Although many non-conventional cylinder liner finishes are now being developed to reduce friction and oil consumption, the effects of surface finish on ring-pack performance is not well understood. A rough surface flow simulation program was developed to calculate flow and stress factors that adjust the solution of the Reynolds equation for the effects of surface roughness as has been done in the literature. Rough surface contact between the ring and liner was modeled using a previously published methodology for asperity contact pressure estimation between rough surfaces. The surface-specific flow and stress factors and asperity contact model were used in conjunction with MIT's previously developed ring-pack simulation program to predict the effects of different surface textures on ring-pack behavior. Specific attention was given to the effects of honing groove cross-hatch angle on piston ring-pack friction in a variety of engine types.

The analytical results suggest that decreasing surface roughness honing cross-hatch angle, such that the cross-hatch grooves are aligned more perpendicular to the flow, reduces ring-pack friction. There are potential adverse effects related to these surface finish modifications including an increase in the engine's susceptibility to scuffing, and an increase in oil consumption. Nonetheless, the model results suggest that decreasing honing cross-hatch angle can significantly reduce predicted ring-pack friction.