Numerical Study on Static and Dynamic Performances of a Double-Pad Annular Inherently Compensated Aerostatic Thrust Bearing

Abstract

The performances of aerostatic bearings have an important impact on machining accuracy in the ultraprecision machine tools. In this paper, numerical simulation is performed to calculate the static and dynamic performances of a double-pad annular inherently compensated aerostatic thrust bearing, while considering the effects of the upper bearing and lower bearing. The static results calculated by the computational fluid dynamics (CFD) method are compared with the finite difference method (FDM) for the specific model. By using polynomial fitting, the load-carrying capacity (LCC) of the bearing is calculated and the relationship between eccentricity ratio, design parameters, and static stiffness is analyzed. The active dynamic mesh method (ADMM) is applied to obtain the dynamic performance of the double-pad aerostatic thrust bearing based on the perturbation theory. Meanwhile, the effects of supply pressure, orifice diameter, squeeze number, and eccentricity ratio are comprehensively considered. Moreover, the step response of the double-pad thrust bearing is analyzed by using the passive dynamic mesh method (PDMM) based on dynamic equation. Related dynamic parameters including natural frequency are obtained through a system identification toolbox with Matlab, which can be used to avoid resonance. It is found that the dynamic calculation results computed by the ADMM and the PDMM are very close. The proposed method can be used to provide guidance for the design and optimization of the double-pad aerostatic thrust bearings.