Dynamic Analysis of a Rotor-Journal Bearing System with Large Dynamic Loads65 (Stiffness and Damping Coefficient Variations in Bearing Oil Films)

Abstract

This paper describes the variations in stiffness and damping coefficients in bearing oil films under the influence of large dynamic loads. A rotor-journal bearing system in which large dynamic loads act on the rotor is nonlinear, so it is analyzed as a coupled problem of the equations of motion for the rotor combined with Reynolds equations for all the bearings. By making use of the displacements and velocities of the rotor center obtained through analysis, the stiffness and damping coefficients have been numerically calculated as an unsteady state along the locus of the rotor center. The variations in these coefficients over one rotor revolution are shown for the journal bearings in a rotary compressor. Our results demonstrate that most of the coefficients for all the bearings vary by more than one order of magnitude, and that oil film nonlinearities seriously influence the rotor motion. © 1993, The Japan Society of Mechanical Engineers. All rights reserved.