Nonlinear Study of a Misaligned Hydrodynamic Journal Bearing

Abstract

Hydrodynamic/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The main objective of this paper is to study the nonlinear effects in a hydrodynamic journal bearing with special attention to the effects of journal axial misalignment. The numerical model that couples the Reynolds equation with the dynamics of the rotor is solved by means of a finite difference solution technique. Fluid film pressures that resulted from an iterative scheme are integrated to generate bearing supporting forces. A two-dimensional Newton-Raphson iteration method is used to locate the journal equlibrium position from which both linear and nonlinear bearing stiffness are evaluated by means of the small perturbation technique. The effects of axial misalignment on bearing equilibrium position, lubricant fluid film thickness, pressure distribution, and stiffness cha...