Modelling of Elastohydrodynamic Journal Bearing with Ultra-Small Clearances

Abstract

This paper presents the numerical calculation for the elastohydrodynamic journal bearing with ultra-small clearances (with the eccentricity ratios approaching unity), where in a local small area only the physically adsorbed layer is present, while in the other areas the sandwich film is present. It is shown that both the adsorbed layer and the elastic deformation of the surface strongly influence the performance of the bearing. For a given operating condition, the surface elastic deformation causes significant reductions in both the maximum hydrodynamic pressure and the load of the bearing, while it significantly increases the minimum clearance (for a given eccentricity ratio) and the friction coefficient. The surface elastic deformation also increases film stiffness. These effects are strongly dependent on the fluid-surface interaction; the stronger the fluid-surface interaction, the more significant the effect of the surface elastic deformation. The present study shows the considerable benefit of the adsorbed layer formed by the strong fluid-surface interaction in increasing the bearing minimum clearance (for a given load or a given eccentricity ratio) and reducing the friction coefficient of the bearing when the surface elastic deformation is involved.