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Research Papers: Gas Turbines: Structures and Dynamics

Design and Manufacturing of Mesoscale Tilting Pad Gas Bearings for 100–200 W Class PowerMEMS Applications

[+] Author and Article Information
Daejong Kim1

Mechanical and Aerospace Engineering, University of Texas at Arlington, 500 West First Street, Woolf Hall, Arlington, TX 76019daejongkim@uta.edu

Aaron M. Rimpel

Department of Mechanical Engineering, Texas A&M University, 3123 TAMU, College Station, TX 77843

Suk Sang Chang, Jong Hyun Kim

Pohang Accelerator Laboratory, POSTECH, San31 Hyojadong, Pohang 790-784, Republic of Korea

1

Corresponding author.

J. Eng. Gas Turbines Power 131(4), 042503 (Apr 10, 2009) (11 pages) doi:10.1115/1.3077646 History: Received December 16, 2007; Revised October 27, 2008; Published April 10, 2009

This paper introduces a design and manufacturing of mesoscale flexure pivot tilting pad gas bearing with a diameter of 5 mm and a length of 1–2.5 mm for PowerMEMS (micro electromechanical systems for power generation) applications with power ranges of 100–200 W. Potential applications include power source for unmanned air vehicles, small robots, microgas turbines to be harnessed by very small solid oxide fuel cells, microblowers/compressors for microfuel cells, etc. The design studies involve scaling analysis, time-domain orbit simulations for stability analyses, and frequency-domain modal analyses for prediction of rotor-bearing natural frequencies. Scaling analysis indicates that direct miniaturization of macroscale tilting pad gas bearing can result in a large bearing number, which may render the rotor-bearing system unstable. However, the scaling analysis provides the baseline design from which the final design can be derived considering manufacturing issue. The generalized modal analysis using impedance contours predict damped natural frequencies close to those from orbit simulations, providing high fidelity to the developed numerical methods. It was predicted that the designed mesoscale tilting pad gas bearings would show very stable operation up to a maximum simulated speed of 1,000,000 rpm. The designed mesoscale tilting pad gas bearings were manufactured using X-ray lithography and electroplating.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Principle of tilting pad gas bearing and EDM machined four pad flexure pivot tilting pad gas bearing: (a) schematic of tilting pad gas bearing and (b) photo of flexure pivot tilting pad gas bearing

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Figure 2

Lithography components of mesoscale flexure pivot tilting pad gas bearing (bearing diameter 2R=5 mm and length L=2.5 mm). The elements within the dotted ellipse represent the pad radial spring and damper.

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Figure 3

Mesoscale flexure pivot tilting pad gas bearing after assembly into bearing sleeve

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Figure 4

Coupled behavior of pad tilting and tangential motion by pressure on a pad

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Figure 5

Photo of X-ray mask for manufacturing of the mesoscale tilting pad gas bearings. Dark area is X-ray transparent material (represents the areas for bearing structures) and bright area is with X-ray absorber (Au film).

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Figure 6

SEM images of the manufactured mesoscale tilting pad gas bearing before assembly into bearing sleeve. Scale bar corresponds to 3 mm in full scale.

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Figure 7

Optical image of 2.0 mm thick mesoscale tilting pads gas bearing (a) 600,000 rpm, (b) 800,000 rpm, and (c) 1,000,000 rpm

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Figure 8

Selected steady state orbits at different speeds

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Figure 9

Trace of εX in nondimensional time τ=ωt, 800,000 rpm (a) 500,000 rpm, (b) 600,000 rpm, (c) 700,000 rpm, and (d) 800,000 rpm

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Figure 10

Modal impedance curves at different speeds

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Figure 11

Details of arc beam spring and damper (dotted ellipse in Fig. 2)

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