Generalized Newtonian Fluids as Lubricants in the Hydrodynamic Conical Bearings – A CFD Analysis

Abstract

Additives, ageing or wear and impurities can cause, that relationship between shear stress and shear rate in a lubricating oil is or becomes non-linear, and due to this, a significant change in the values of operating parameters of slide hydrodynamic bearings may occur. It is important to take into account such dependence during design and simulations of slide bearings. The calculations, which consider the non-linear properties of the lubricating oil, can be carried out by adopting the generalized Newtonian fluid models. This paper shows the result of CFD simulation of slide conical bearings hydrodynamic lubrication, assuming that the lubricating oil behaves as a generalized Newtonian fluid. The hydrodynamic pressure distributions, load carrying capacities and friction torques were calculated for bearings lubricated with different types of generalized Newtonian fluids and the obtained data were compared. In the study, the following models of fluids were adopted: the Power-law fluid (Ostwald-de Waele), the Cross fluid and the Carreau fluid. The coefficients of mentioned relationships were determined by fitting the curves described by each model to the experimental data using the least squares approximation method. The calculations of hydrodynamic pressure distributions, load carrying capacities and friction torques were carried out using the commercial CFD software Ansys Fluent from the Ansys Workbench 2 platform.