Analysis of the Combined Effect of the Surface Roughness and Inertia on the Performance of High-Speed Hydrostatic Thrust Bearing

Abstract

The combined effects of surface roughness and rotational inertia on the performance of high speed hydrostatic thrust bearings are presented theoretically in this paper. A deterministic three-dimensional roughness model is introduced to derive the function of film thickness. Both the simplified Reynolds equation with rotational inertia effect and the recess flow continuity equation with recess volume fluid compressibility effect are deduced to govern the lubrication model. The static performance parameters of bearing are obtained, such as the load capacity, the flow rate and the frictional power. Employing a small perturbation method, the dynamic coefficients of bearing are also evaluated. According to the results, it is shown that the surface roughness has a negligible influence on the load capacity, but provides a significant effect on the flow rate and the dynamic stiffness and damping coefficients; and for the same load capacity, the longitudinal roughness pattern generates a higher frictional power comparing to the transverse or isotropic pattern; and the transverse roughness pattern reduces the required lubricant flow rate and increases the value of dynamic coefficients; however, this trends are reversed for the longitudinal roughness pattern.