Numerical Simulation and Experimental Verification of the Stiffness and Stability of Thrust Pad Aerostatic Bearings

Hai-Long Cui,Yang Wang,Huan Xia,Hong Yang,Bao-Rui Wang

doi:10.1186/s10033-018-0228-3

Hai-Long Cui, Yang Wang + Show 3 more

Open Access

https://doi.org/10.1186/s10033-018-0228-3

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Abstract

Many researchers concentrate on improving the stiffness and stability of aerostatic bearings, however the contradiction between stiffness and stability is still existed. Therefore, orifice, multiple, and porous restrictors are designed to illustrate the influence of restrictor characteristics on the stability and stiffness of the aerostatic circular pad bearings. Because both the stiffness and stability of aerostatic bearings are determined by the internal pressure distribution, the full Navier-Stokes (N-S) equations are applied to solve internal pressure distribution in bearing film by using computational fluid dynamics (CFD) method. Simulation results present that the stiffness and stability of aerostatic circular pad bearings are influenced significantly by geometrical and material parameters, such as film thickness, orifice diameters, and viscous resistance coefficient. Verified by the experimental data, the micro vibration of orifice restrictor is almost the same as multiple restrictors with amplitude of 0.02 m/s2, but it is much stronger than the porous restrictors with acceleration of 0.006 m/s2. The optimal stiffness of multiple restrictors increased by 46%, compared to only 30.2 N/μm of orifice restrictor, and the porous restrictors had obvious advantage in the small film thickness less than 6 μm where the optimal stiffness increased to 38.3 N/μm. The numerical and experimental results provide guidance for improving the stiffness and stability of aerostatic bearings.

Highlights

Aerostatic bearings, which are nearly frictionless, require low driving power and possess high accuracy of movement, have been widely used in ultra-precision machine tools
With regard to the static and dynamic characteristics of aerostatic bearings, stiffness and stability play a key role in achieving nanometer-level motion precision
Gao et al [6] conducted the influence the chamber shape on performance characteristics of aerostatic thrust bearings, and found that the pressure depression, gas vortices, and the turbulent intensity which were all weakened with decreasing air film thickness

Summary

Introduction

Aerostatic bearings, which are nearly frictionless, require low driving power and possess high accuracy of movement, have been widely used in ultra-precision machine tools. Over the last few years, published research focuses largely on the stiffness characteristics of aerostatic bearings with orifice restrictors. Increasing the stiffness of aerostatic bearings with orifice restrictors increases micro vibration. Charki et al [24] found that the stiffness of aerostatic bearings with multiple restrictors could be improved because of the smaller pressure drop near the gas inlet. Published literatures reveal that there are not comprehensive studies considering the influences of different restrictor characteristics on the stiffness and stability of aerostatic bearings. Porous restrictors and multiple restrictors were designed to improve the stability and stiffness of aerostatic circular pad bearings in this paper. The influence of film thickness, orifice diameter, and material parameters on the stiffness and stability of the aerostatic circular pad bearings was investigated. The accuracy of the numerical simulation results was verified by the experimental data

Numerical Modeling

Design variable

Results and Discussion