Parameter Sensitivity Analysis on Dynamic Coefficients of Partial Arc Annular-Thrust Aerostatic Porous Journal Bearings

Polina Khan,Seok-Won Kang,Pyung Hwang

doi:10.3390/app112210791

Polina Khan, Seok-Won Kang + Show 1 more

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https://doi.org/10.3390/app112210791

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Abstract

Aerostatic bearings are widely used in high-precision devices. Partial arc annular-thrust aerostatic porous journal bearings are a prominent type of aerostatic bearings, which carry both radial and axial loads and provide high load-carrying capacity, low air consumption, and relatively low cost. Spindle shaft tilting is a resource-demanding challenge in numerical modeling because it involves a 3D air flow. In this study, the air flow problem was solved using a COMSOL software, and the dynamic coefficients for tilting degrees of freedom were obtained using finite differences. The obtained results exhibit significant coupling between the tilting motion in the x-and y-directions: cross-coupled coefficients can achieve 20% of the direct coefficient for stiffness and 50% for damping. In addition, a nonlinear behavior can be expected, because the tilting motion within 3°, tilting velocities within 0.0012°/s, and relative eccentricity of 0.2 have effects as large as 20% for direct stiffness and 100% for cross-coupled stiffness and damping. All dynamic coefficients were fitted with a polynomial of eccentricity, tilting, and tilting velocities in two directions, with a total of six parameters. The resulting fitting coefficient tables can be employed for the fast dynamic simulation of the rotor shaft carried on the proposed bearing type.

Highlights

Porous aerostatic bearings are widely used in machinery, owing to their relatively high load-carrying capacity and low air consumption [1,2,3]
Similar to other types of aerostatic bearings, owing to their high accuracy and zero contamination, they are suitable for high-precision devices
The tilting motion greatly affects the bearing forces, as well as other types of air film distortions, which are widely considered in recent publications

Summary

Introduction

Porous aerostatic bearings are widely used in machinery, owing to their relatively high load-carrying capacity and low air consumption [1,2,3]. The friction drag of a porous aerostatic bearing is low [4,5], its motion accuracy is higher than that of a conventional orifice-type aerostatic bearing [5,6], and its load thresholds at high rotation speeds are the highest among other types of aerostatic bearings [5,7]. The amount of porous material required can be reduced via design optimization [8]. The optimal governing equations required for porous air bearing analysis remain under discussion. Zhong et al [9] experimentally determined Ergun’s equation coefficients for the pressure drop in sintered metal porous media for air bearings. Zhong et al [11]

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