Dynamic Coefficients of the Coupled Journal and Thrust Bearings Considering Five Degrees of Freedom for a General Rotor-Bearing System

This paper proposes a method to calculate the stiffness and the damping coefficients of the coupled journal and thrust bearings considering tilting motion. The Reynolds equations and their perturbation equations are derived by linearization of bearing reaction with respect to the general five degrees of freedom, i.e. the tilting displacement and angular velocity as well as the translational displacement and velocity. Reynolds equations and their perturbation equations are transformed to the finite element equations by considering the continuity of pressure and flow at the interface between the journal and the thrust bearings. It also includes the Reynolds boundary condition in the numerical analysis to simulate the cavitation phenomena. The stiffness and the damping coefficients of the proposed method are compared with those of the numerical differentiation of the loads with respect to finite displacements and velocities of bearing center. It shows that the proposed method can calculate the dynamic coefficients of a coupled journal and thrust bearing more accurately and efficiently than the differentiation method.