Method for Calculating Stiffness and Damping Coefficients of Hybrid Bearings Based on Dynamic Mesh Model

Abstract

For the reason that Reynolds equation is not suitable for reflecting nonlinear flow mechanics coupled by inertial effect of oil circumferential flow,squeeze effect of the journal,and diffusion effect of oil entry flow,the calculating accuracy of stiffness and damping coefficients can not satisfy optimal design of high speed bearings.A new approach of calculating stiffness and damping coefficients of journal bearings is developed based on Navier-Stokes equation.The changing oil film force,the displacement perturbation,the velocity perturbation and the rotating speed are achieved by usiug user definition function programs.The moving boundary of the journal caused by rotational movement is changed into static boundary for avoiding the grid distortion.The coordination of moving grid caused by displacement perturbation and velocity perturbation is updated by the spring smoothing theoretical model.Comparing oil film force under steady condition with those of transient processes,the value scope of displacement perturbation and velocity perturbation are defined.The stiffness and damping coefficients of a typical bearing are calculated by applying the approach combined with the perturbation theory,and the dynamic development process of oil film thickness and three-dimensional pressure distribution are achieved.Finally,an experiment is used to test the stiffness coefficients of the bearing based on the influence coefficient method,which are substantial in agreement with theoretical analysis.The results show that the numerical method is valid.