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Research Papers: Gas Turbines: Structures and Dynamics

The Numerical and Experimental Characteristics of Multimode Dry-Friction Whip and Whirl

[+] Author and Article Information
Jason C. Wilkes

Turbomachinery Laboratory, Texas A&M University, College Station, TX 77802jasonwilkes@tamu.edu

Dara W. Childs

Turbomachinery Laboratory, Texas A&M University, College Station, TX 77802dchilds@tamu.edu

Benjamin J. Dyck

Turbomachinery Laboratory, Texas A&M University, College Station, TX 77802bjdyck@chevron.com

Stephen G. Phillips

Turbomachinery Laboratory, Texas A&M University, College Station, TX 77802sphillips@tamu.edu

J. Eng. Gas Turbines Power 132(5), 052503 (Mar 04, 2010) (9 pages) doi:10.1115/1.3204658 History: Received March 30, 2009; Revised May 12, 2009; Published March 04, 2010; Online March 04, 2010

The nature of dry-friction whip and whirl is investigated through experimental and numerical methods. A test rig was designed and constructed to demonstrate and record the character of multimode dry-friction whip and whirl. These tests examined steady-state whip and whirl characteristics for a variety of rub materials and clearances. A simulation model was constructed using tapered Timoshenko beam finite elements to form multiple-degree-of-freedom rotor and stator models. These models were reduced by component mode synthesis to discard high-frequency modes while retaining physical coordinates at the rub location to model rotor-stator interaction using a nonlinear contact model with Coulomb friction. Simulations were performed for specific test cases, and compared against experimental data; these comparisons are favorable. Experimental data analysis showed multiple whirl and whip regions, despite claims of previous investigators that these regions are predicted analytically but not produced in simulations or experiments. Spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Geometric model governing rotor-stator contact

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Figure 2

Rotor-stator interaction model after Ref. 14

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Figure 3

General case of the U-shaped plot attributed to black

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Figure 4

Multimode dry-friction whirl prediction for Bartha’s rig (14)

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Figure 5

Picture of the TAMU whip and whirl test rig

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Figure 6

Section view of the TAMU whip and whirl test rig

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Figure 7

Section view of the TAMU whip and whirl test rig rotor

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Figure 8

XLTRC2 simulation model for the TAMU whip and whirl rig

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Figure 9

Measured (a) frequency and (b) amplitude of the primary backward whirl component at probe 1 for a test case having R/Cr=246

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Figure 10

Two-sided FFT of probe 1 measurements for a speed decreasing case of dry-friction whip and whirl, recorded during a test case having R/Cr=246

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Figure 11

Measured backward precession frequency versus rotor speed at probe 1 for a test case having R/Cr=238

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Figure 12

Spectrogram for speed increasing whirl/whip for a test case having R/Cr=238, showing excitation of higher whirl modes by sideband harmonics

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Figure 13

Measured backward precession amplitude versus speed for a test case having R/Cr=246

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Figure 14

Measured backward precession amplitude relative to probe 1 versus speed for a test case having R/Cr=246

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Figure 15

Measured and predicted relative mode shapes at (a) 130 rpm and (b) 235 rpm for a test case having R/Cr=246

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Figure 16

Measured probe and accelerometer orbits in (a) the first whirl region, (b) the first whip region, (c) the third whirl region, and (d) the third whip region for a test case having R/Cr=246

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Figure 17

Measured PFR versus rotor speed for 660 Bronze bearing with a measured R/Cr=517

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Figure 18

Measured PFR versus rotor speed for Babbitt bearing with R/Cr=517

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Figure 19

Comparison of measured and predicted backward precession frequencies for a 660 Bronze bearing having R/Cr=385

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Figure 20

Frequency spectra for simulation of 660 Bronze bearing having R/Cr=385 at probe 1

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Figure 21

Predicted backward precession amplitude versus speed for a 660 Bronze bearing having R/Cr=385

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