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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Dynamic Properties of Tilting-Pad Journal Bearings: Experimental and Theoretical Investigation of Frequency Effects due to Pivot Flexibility

[+] Author and Article Information
Waldemar Dmochowski

Institute for Aerospace Research, Gas Turbine Laboratory, National Research Council, Building M-17, 1200 Montreal Road, Ottawa, Ontario Canada K1A 0R6waldek.dmochowski@nrc-cnrc.gc.ca

J. Eng. Gas Turbines Power 129(3), 865-869 (Sep 01, 2006) (5 pages) doi:10.1115/1.2436574 History: Received July 21, 2006; Revised September 01, 2006

Tilting-pad journal bearings (TPJBs) dominate as rotor supports in high-speed rotating machinery. The paper analyzes frequency effects on the TPJB’s stiffness and damping characteristics based on experimental and theoretical investigations. The experimental investigation has been carried out on a five pad tilting-pad journal bearing of 98mm in diameter. Time domain and multifrequency excitation has been used to evaluate the dynamic coefficients. The calculated results have been obtained from a three-dimensional computer model of TPJB, which accounts for thermal effects, turbulent oil flow, and elastic effects, including that of pad flexibility. The analyzes of the TPJB’s stiffness and damping properties showed that the frequency effects on the bearing dynamic properties depend on the operating conditions and bearing design. It has been concluded that the pad inertia and pivot flexibility are behind the variations of the stiffness and damping properties with frequency of excitation.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Journal bearing dynamic test rig

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Figure 2

Coordinate systems: (a) attached to shaft center; and (b) attached to pad center

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Figure 3

Typical pivot stiffness of a 100mm TPJB

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Figure 4

Mass, spring, and damper elements for tilting pad

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Figure 5

Coherence function Fy and Y

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Figure 6

Bearing direct stiffness coefficients: Case 1: (a) horizontal; and (b) vertical

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Figure 7

Bearing direct damping properties: Case 1: (a) horizontal; (b) vertical

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Figure 8

Calculated bearing stiffness coefficients: Case 2: (a) horizontal; (b) cross-coupling; and (c) vertical

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Figure 9

Calculated bearing damping properties: Case 2: (a) horizontal; (b) cross-coupling; and (c) vertical

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