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Research Papers: Gas Turbines: Structures and Dynamics

A Rotordynamic, Thermal, and Thrust Load Performance Gas Bearing Test Rig and Test Results for Tilting Pad Journal Bearings and Spiral Groove Thrust Bearings

[+] Author and Article Information
Aaron M. Rimpel

Southwest Research Institute,
San Antonio, TX 78238
e-mail: aaron.rimpel@swri.org

Giuseppe Vannini

Baker Hughes,
Florence 50127, Italy
e-mail: giuseppe.vannini@bhge.com

Jongsoo Kim

Waukesha Bearings Corporation,
Pewaukee, WI 53072
e-mail: jkim@waukbearing.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 21, 2016; final manuscript received July 14, 2017; published online August 16, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(12), 122501 (Aug 16, 2017) (11 pages) Paper No: GTP-16-1259; doi: 10.1115/1.4037315 History: Received June 21, 2016; Revised July 14, 2017

A high-speed gas bearing test rig was developed to characterize rotordynamic, thermal, and thrust load performance of gas bearings being developed for an oil-free turboexpander. The radial bearings (RBs) tested in this paper were tilting pad journal bearings with radial compliance features that allow the bearing bore to increase to accommodate shaft growth, and the thrust bearings (TBs) were a spiral groove type with axial compliance features. The TB accounts for over 90% of the combined bearing power consumption, which has a cubic relationship with speed and increases with case pressure. RB circumferential pad temperatures increased approximately with speed to the fourth or fifth power, with slightly higher temperature rise for lower case pressure. Maximum steady-state bearing pad temperatures increase with increasing speed for similar cooling mass flow rates; however, only the TB showed a significant increase in temperature with higher case pressure. The TBs were stable at all speeds, but the load capacity was found to be lower than anticipated, apparently due to pad deformations caused by radial temperature gradients in the stator. More advanced modeling approaches have been proposed to better understand the TB thermal behavior and to improve the TB design. Finally, the RBs tested were demonstrated to be stable up to the design speed of 130 krpm, which represents the highest surface speed for tilting pad gas bearings tested in the literature.

Copyright © 2017 by ASME
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Figures

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Fig. 3

Computer-aided design model of gas bearing test rig: (a) external view and (b) cross section

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Fig. 4

Schematic of air flow loop

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Fig. 5

Bearing internal cooling flow configurations

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Fig. 6

Bearing pad thermocouples

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Fig. 7

Combined bearing power loss for different speeds and case pressures

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Fig. 8

Average RB circumferential pad temperature rise from leading to trailing edge

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Fig. 9

Maximum steady-state bearing pad temperatures for different speeds and case pressures: (a) RB pad temperatures and (b) TB pad temperatures

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Fig. 10

TB pad temperatures during low case pressure test, no external thrust load

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Fig. 11

Relative rotor axial position versus speed during low case pressure test, no external thrust load

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Fig. 12

Identification of internal thrust force at 80 krpm and low case pressure

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Fig. 13

Waterfall plot of vibration during load capacity test: (a) lateral and (b) axial

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Fig. 14

Thermal response of loaded TB during load capacity test

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Fig. 15

Waterfall plot of lateral vibration during final shut down: (a) sampled at 10 kHz for 0.32 s and (b) sampled at 10 kHz for 0.04 s

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Fig. 16

Orbit plots at different points of final shut down: (a) point A, (b) between A and B, and (c) between C and D

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Fig. 17

RB pad temperatures during final shut down

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Fig. 18

Photograph of RB showing condition of pad coating and yielded radial compliance feature

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Fig. 19

Bearing condition before and after yielding

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Fig. 20

Gas journal bearing operating speed experience

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