Inertia Effects in a Hybrid Bearing With a 45 Degree Entrance Region

Abstract

An investigation is presented that illustrates the effects of inertia on the flow and pressure field throughout a hybrid hearing with a 45 degree entrance region. This type of bearing has been previously shown to offer better performance over the hybrid bearing with a normal entry region. A two-dimensional planar approach is adopted and the resulting flow governing equations are solved using the Galerkin Weighted Residual finite element method. This algorithm incorporates an advanced streamline upwinding method to evaluate the nonlinear effects of the convection terms. The results demonstrate the complex nature of the velocity field and its subsequent impact on the pressure field. This comprehensive parametric study also shows why traditional lubrication approaches that typically exclude convection effects will become unreliable at high operating speeds of turbomachinery. A set of loss coefficients modeling the pressure ‘ram’ effects are provided to illustrate the inertia effects in the entrance region of the film lands. In a hybrid bearing, these effects have to be characterized according to the operating parameters of the bearing and the journal direction of rotation.