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Research Papers: Hydrodynamic Lubrication

Thermohydrodynamic Analyses of Bump Air Foil Bearings With Detailed Thermal Model of Foil Structures and Rotor

[+] Author and Article Information
Donghyun Lee, Daejong Kim

Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, 500 W. 1st Street, Arlington, TX 76019

J. Tribol 132(2), 021704 (Apr 14, 2010) (12 pages) doi:10.1115/1.4001014 History: Received July 28, 2009; Revised January 11, 2010; Published April 14, 2010; Online April 14, 2010

A new thermohydrodynamic analysis model for bump air foil bearings with a detailed thermal model of bump foil structures and rotor is presented. In the developed model, temperatures of lubricating air film, top foil, bump foils, bearing sleeve, and rotor are calculated simultaneously through an iterative process. Reynolds equation and 3D energy equation were applied to the air film, and energy equations were applied to all the other structures around the bearing. Energy and momentum equations were applied to cooling channels to predict spatial temperature distribution along the cooling channels. The thermal growth of the rotor, foil structure, bearing sleeve, and centrifugal growth of the rotor are also considered. For the accuracy of the model, effective heat transfer resistance between the top foil and bearing sleeve was measured for various conditions and implemented into the thermal analysis around the cooling channels. The model was also bench marked with published experimental results for verifications. Using a developed model, parametric studies were performed with different bearing nominal clearances, applied loads, rotating speeds, and cooling conditions through channels.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Description of typical air foil bearings

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Figure 2

Schematics of thermal subsystem of rotor and foil bearing

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Figure 3

Thermal model of foil structure: (a) foil structure and (b) heat transfer mechanism around foil structure

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Figure 4

Photo of air foil bearing

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Figure 5

Photo of the test instrumentation to measure the thermal resistance between the top foil and bearing sleeve

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Figure 6

Measured thermal resistances between top foil and bearing sleeve. (a) Measured temperature when applied pressure is 2.8×103 Pa. (b) Measured thermal resistance for various pressures.

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Figure 7

Nondimensional film pressure (40,000 rpm, C=40 μm, 20 N)

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Figure 8

Rotor temperature along the rotor axis (40,000 rpm, C=40 μm, 20 N)

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Figure 9

Bulk film and top foil temperature distribution (40,000 rpm, C=40 μm, 20 N): (a) bulk film temperature and (b) Top foil temperature

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Figure 10

Temperatures of primary and secondary channels (40,000 rpm, C=40 μm, 20 N): (a) third channel and (b) 13th channel

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Figure 11

Comparison of predicted top foil temperature with test data (31) at 9–170 deg (40,000 rpm)

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Figure 12

Rotor temperature distributions for various clearances (40,000 rpm, 20 N)

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Figure 13

Bearing sleeve temperature for various clearances (40,000 rpm, 20 N)

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Figure 14

Rotor temperature for various loads (40,000 rpm, C=35 μm)

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Figure 15

Bearing sleeve and averaged top foil temperatures for various loads (40,000 rpm, C=35 μm)

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Figure 16

Normalized thermal and centrifugal growths of all the rotor-bearing elements (40,000 rpm, 100 N). (a) Normalized thermal growth of foil structure with respect to C. (b) Normalized thermal and centrifugal growths of rotor and bearing sleeve with respect to C.

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Figure 17

Average rotor and bearing sleeve temperatures for various rotating speeds (C=35 μm, 20 N)

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Figure 18

Bearing sleeve and averaged rotor and top foil temperatures for various pressure drops (40,000 rpm, C=40 μm, 20 N)

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Figure 19

Temperatures of 13th secondary channel and bump for various pressure drops (40,000 rpm, C=40 μm, 20 N)

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Figure 20

Heat transfer in foil bearing for various pressure drops (40,000 rpm, C=40 μm, 20 N). (a) Heat transfer rate from air film to rotor and foil structure. (b) Outgoing heat flux from foil structure to ambient air. (c) Outgoing heat flux through channel.

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Figure 21

Bearing sleeve and averaged rotor and top foil temperature for various convection coefficients of bearing sleeve outer surface (40,000 rpm, C=40 μm, 20 N)

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