An Investigation into the Thermal Effects on a Hydrodynamic Bearing's Clearance

Abstract

The scope of this article is to examine the effects of thermal expansion (up to seizure) on the clearance of a hydrodynamic bearing under prescribed operating conditions. This parametric study uses angular speed, eccentricity, and the journal/bushing material pairings as varying parameters. The study focuses on how the size of the clearance varies with temperature and pressure (elastic deformation) and whether it is possible for a complete thermal lockup (seizure) to occur when certain material pairings are used. The effects of the thermal expansion on the load-carrying capacity, torque, and total deformation of the clearance are presented. Thermal versus mechanical effects domination are also analyzed in order to establish the conditions under which one, or the other become dominant. The present model uses the three-dimensional Navier-Stokes equations and a fully termed energy equation for the fluid coupled in a two-way feedback mode with the 3D energy and the elasticity equations for the bushing and journal. The effects of the viscosity variation with temperature and that of cavitation are also incorporated in the presented results.

KEY WORDS:

• Navier-Stokes; Three-Dimensional; Journal Bearing; Solid-Fluid Interaction; Thermal Effects; Seizure

NOTE

Notes

1 . Three different types of cases are considered: “baseline” refers to a full thermal model (shaft + bushing + fluid) without any deformation; “isothermal” accounts only for solid elastic deformations; and St/St, St/Al, Al/St cases refer to full thermal and thermoelastic deformations.