Research Papers: Applications

Optimization of Groove Geometry for Thrust Air Bearing to Maximize Bearing Stiffness

[+] Author and Article Information
Hiromu Hashimoto

Dean of Graduate School of Engineeringhiromu@keyaki.cc.u-tokai.ac.jp

Masayuki Ochiai

 Tokai University, 1117 Kitakaname, Hiratsuka-shi, Kanagawa-ken, 259-1292, Japan

J. Tribol 130(3), 031101 (Jun 23, 2008) (11 pages) doi:10.1115/1.2913546 History: Received August 10, 2007; Revised March 25, 2008; Published June 23, 2008

Hydrodynamic gas film bearings are widely used for very-high-speed, lightly loaded rotating machinery. In the design of hydrodynamic gas film bearings, it is of cardinal importance to enhance the stiffness of gas films to minimize vibration due to external excitations. Among various types of hydrodynamic gas film thrust bearings, grooved bearings have an advantage of high stiffness and load-carrying capacity, but the stiffness of the bearings strongly depends on groove geometry. Therefore, when the groove geometry is suitably designed, it is expected to considerably improve the stability characteristics of the bearings. However, conventional bearing geometries are based on a fixed logarithmic spiral curve, and there is no literature on how to effectively change the groove geometry to drastically improve the bearing characteristics. In this paper, the entirely new optimum design methodology, in which the groove geometry can be flexibly changed by using the spline function, is presented to maximize the stiffness of gas films for grooved thrust bearings. The effectiveness of the methodology is experimentally verified.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Method of changing groove boundary geometry

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Figure 2

Bearing geometry transformation based on the boundary-fitted coordinate system

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Figure 3

Definition of control volume

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Figure 4

Optimum design variables at W=9.8N

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Figure 5

Groove geometry of bearings and pressure distribution under W=9.8N and ns=40,000rpm

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Figure 6

Comparison of optimized and herringbone bearings

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Figure 7

Variation of bearing characteristics with rotational speed

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Figure 8

Dynamic pressure distributions of imaginary part for W=29.4N and ns=40,000rpm

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Figure 9

Film thickness and spring coefficient with groove depth

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Figure 10

Bearing geometries and various bearing characteristics under constant film thickness condition

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Figure 11

Overview of optimized bearing

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Figure 12

Overview of test rig

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Figure 13

Air film temperature with rotational speed

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Figure 14

Film thickness with rotational speed

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Figure 15

Comparison of measured data with predicted results for W=14.7N

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Figure 16

Spring coefficient with rotational speed



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