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Research Papers: Gas Turbines: Structures and Dynamics

Identification and Prediction of Force Coefficients in a Five-Pad and Four-Pad Tilting Pad Bearing for Load-on-Pad and Load-Between-Pad Configurations

[+] Author and Article Information
Adolfo Delgado, Bugra Ertas, Michael Drexel

Structural Dynamics Laboratory, GE Global Research Center, Niskayuna, NY 12309

Giuseppe Vannini, Lorenzo Naldi

Conceptual Advanced Mechanical Design, GE Oil & Gas, Florence, Italy 50127

J. Eng. Gas Turbines Power 133(9), 092503 (Apr 19, 2011) (9 pages) doi:10.1115/1.4002864 History: Received May 09, 2010; Revised July 31, 2010; Published April 19, 2011; Online April 19, 2011

This paper presents the identification of the rotordynamic force coefficients for direct lubrication five-pad and four-pad tilting pad bearings. The bearing is 110 mm in diameter with a L/D of 0.4 pad axial length (44 mm). The experiments include load-on-pad and load-between-pad configurations, with 0.5 and 0.6 pivot offsets, for rotor speeds ranging from 7500 rpm to 15,000 rpm. The bearing force coefficients are identified from multiple frequency excitations (20–300 Hz) exerted on the bearing housing by a pair of hydraulic shakers and are presented as a function of the excitation frequency and rotor speed for a 300 kPa unit load. The experimental results also include temperatures at the trailing edge of three pads. The direct force coefficients, identified from curve-fits of the complex dynamic stiffness, are frequency independent if considering an added mass term much smaller than the test device modal mass. The force coefficients from the four-pad bearing load-between-pad configuration show similar coefficients in the loaded and orthogonal directions. On the other hand, as expected, the five-pad bearing load-on-pad shows larger coefficients (25%) in the loaded direction. The maximum pad temperature recorded for the 0.5 pivot offset configurations is up to 20°C higher than those associated to the 0.6 offset configuration. Results from a predictive code are within 50% of the experimental results for the direct stiffness coefficients and within 30% for the direct damping coefficients.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic view of component level test rig including detailed view of bearing housing

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Figure 2

Test bearings: four- and five-pad tilting pad bearing configurations

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Figure 3

Real part of dynamic impedances for five-pad, 0.5 and 0.6 offset, LOP, 300 kPa bearing configuration

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Figure 4

Imaginary part of complex dynamic stiffness for five-pad, 0.5 and 0.6 offset, LOP, 300 kPa configuration

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Figure 5

Stiffness predictions versus measurements for a five-pad bearing, LOP, 300 kPa, 0.5 and 0.6 offset

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Figure 6

Damping predictions versus measurements for a five-pad bearing, LOP, 300 kPa, 0.6 offset

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Figure 7

Trailing edge temperatures for LOP configuration, 0.5 and 0.6 offset, 300 kPa

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Figure 8

Real part of complex dynamic stiffness for four-pad, (a) 0.5 and (b) 0.6 offset, 300 kPa, LBP configuration

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Figure 9

Imaginary part of complex dynamic stiffness for 4 pads: (a) 0.5 and (b) 0.6 offset, 300 kPa, LBP configuration

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Figure 10

Stiffness predictions versus measurements for a four-pad bearing, LBP, 300 kPa, 0.5 offset

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Figure 11

Damping predictions versus measurements for a four-pad bearing, LBP, 300 kPa, 0.6 offset

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Figure 12

Trailing edge temperatures for LBP configuration, 0.5 and 0.6 offsets, 300 kPa

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