TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Field Methods for Identification of Bearng Support Parameters—Part I: Identification From Transient Rotor Dynamic Response due to Impacts

[+] Author and Article Information
Oscar C. De Santiago

 Dresser-Rand Company, Olean, NY 14760desantiago@dresser-rand.com

Luis San Andrés

 Texas A&M University, College Station, TX 77843-3123lsanandres@mengr.tamu.edu

This condition assumes identical bearing supports, similar lubricant operating conditions and equal static load.

J. Eng. Gas Turbines Power 129(1), 205-212 (Mar 01, 2003) (8 pages) doi:10.1115/1.2227033 History: Received October 01, 2002; Revised March 01, 2003

A simple procedure, with the potential as a field resource, for identification of a bearing support parameter from recorded transient rotor responses due to impact loads follows. The method is applied to a test rotor supported on a pair of mechanically complex bearing supports, each comprising a tilting pad bearing in series with an integral squeeze film damper. Identification of frequency dependent bearing force coefficients is good at a rotor speed of 2000 rpm. Stiffness coefficients are best identified in the low frequency range (below 25 Hz) while damping coefficients are best identified in the vicinity of the first natural frequency (48 Hz) of the rotor bearing system. The procedure shows that using multiple-impact frequency averaged rotor responses reduces the variability in the identified parameters. The identification of frequency-dependent force coefficients at a constant rotor speed is useful to assess rotor-bearing system stability.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Test apparatus used for bearing parameter identification and special fixture used to deliver impacts

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Figure 2

Combined integral damper and flexure pivot bearing used for parameter identification

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Figure 3

Digital vibration signal filtering. (a) Original time record and time-based filtered signal; (b) DFT of filtered signal and comparison with a frequency-based synchronized filter.

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Figure 4

Identified frequency-dependent bearing force coefficients and comparison with predicted parameters for the combined ISFD-FPJB bearing support. (a) Direct force coefficients; (b) cross-coupled force coefficients.

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Figure 5

Identified direct stiffness and damping coefficients as a function of the number of (impact) paired responses used. Operating condition: rotor speed=20,000.

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Figure 6

Comparison of measured and predicted rotor forced response at bearing locations. Impact in horizontal direction.




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