A Theory of the Hydrodynamic Film Thickness in Centrally Pivoted Oil-Lubricated Plane-Pad Thrust Bearings

Abstract

An analytical model is developed in this article for pivoted, oil-lubricated rectangular plane-pad thrust bearings considering the thermal effects of oil viscosity. The model is governed by three dimensionless parameters: the pad length-to-width ratio, the location of the pad pivot, and the bearing load parameter that prescribes lubricant thermal properties and applied load. Analyses were carried out for centrally pivoted bearings of a number of pad length-to-width ratios and a number of bearing load parameters. The results suggest a theory that, for bearings with a square pad or wider, the oil viscosity thermal effect enables a centrally pivoted bearing to develop a hydrodynamic film thickness of about one half of the film thickness that would be developed under isothermal conditions with the pad pivoted at its maximum-load-capacity optimal position. This level of relative film thickness could be developed under all design conditions of practical interest. The theory is fairly general and may be applicable to fan-shaped thrust bearing assemblies with the concept of equivalent length-to-width ratio of the bearing pad. The validity of the theory is modestly evaluated and should be further validated in time through various means and in various settings.