Flow factor modeling of combustion engine ring and cylinder components in mixed hydrodynamic lubrication

Abstract

This work employees the modification of the Reynolds equation for computational efficiency by analyzing rough surfaces in the hydrodynamic flow regime through the use of flow factors. This analysis is aimed towards modeling the surface interactions and pressure variations across power cylinder components of an internal combustion engine, namely the piston ring and cylinder wall. The Patir and Cheng equations are for general surfaces that accounts for the overall effect of roughness and anisotropic structure. However, rough surfaces are not fully characterized by these two parameters and therefore the aim of this paper was to provide flow-factors specific to the cross-hatched cylinder liner surfaces and piston ring interface. These interacting surfaces were measured directly through the use of a profilometer. Average flow factors are derived via full deterministic solution of the Reynolds equation over rough surfaces to model the pressure and shear variations relative to smooth surfaces. These flow factors can then be used to consider the effect of roughness in lubrication problems without deterministically modeling roughness.

A Mixed Lubrication Model of Piston Rings on Cylinder Liner Contacts Considering Temperature-Dependent Shear Thinning and Elastic–Plastic Contact

“…Their method assumes that rough surface heights are a perfect Gaussian distribution though. This work uses the flow factors Locker et al [45] derived for an actual crosshatched cylinder wall by combining stochastic concepts with Peklinik's signal processing theory [33].…”

“…Locker et al [45] used deterministic modeling of flow around the measured rough surfaces of a ring a cylinder to find the averaged flow factors over the entire surface and fitted empirical equations to the predicted flow factors:…”