Rotordynamic Force Coefficients for a New Damper Seal Design

[+] Author and Article Information
Bugra H. Ertas

Rotating Equipment Group, Vibrations & Dynamics Laboratory, GE Global Research Center, Niskayuna, NY 12309ertas@research.ge.com

John M. Vance

Turbomachinery Laboratory, Mechanical Engineering Department, Texas A&M University, College Station, TX 77843-3123jvance@tamu.edu

J. Tribol 129(2), 365-374 (Nov 03, 2006) (10 pages) doi:10.1115/1.2464138 History: Received April 17, 2006; Revised November 03, 2006

The objective of the following work was to determine frequency-dependent rotordynamic force coefficients for a new annular gas damper seal design. Both rotating and nonrotating experimental tests are presented for inlet pressures at 1000psig(69bar), a frequency excitation range of 20300Hz, and rotor speeds up to 15,200rpm. Two different testing methods were used for determining coefficients: (1) dynamic pressure response method and (2) mechanical impedance method. The dynamic pressure method required the measurement of internal seal cavity pressure modulations in combination with the vibratory motion, whereas the mechanical impedance method used the measurement of external shaker forces, accelerations, and motion of the mechanical system. In addition to the new fully partitioned damper seal (FPDS) tests, the same experiments were conducted for a conventional pocket damper seal (PDS) design. Results of the frequency-dependent force coefficients and the internal seal dynamics for the two different gas damper seals are compared. The conclusions of the tests show that the FPDS design possesses significantly more positive direct damping and direct stiffness compared to the conventional PDS. The experiments also show the measurement of same-sign cross-coupled (cross-axis) stiffness coefficients for both seals, which indicate that the seals do not produce a destabilizing influence on rotor-bearing systems.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Annular gas seals in a straight-through compressor

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Figure 2

Gas damper seals: Six bladed conventional PDS versus FPDS

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Figure 3

High-pressure seal test rig (7)

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Figure 5

Experimental measurements and cross-sectional views

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Figure 6

Experimental measurements: Mechanical impedance method (7)

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Figure 7

Cavity orientation and coordinate axis

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Figure 8

Static and dynamic pressure transducer installation: Single row of cavities

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Figure 9

Experimental measurements: Dynamic pressure response method FP PDS

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Figure 10

Stand-alone cavities: Diverging and converging configurations

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Figure 11

Phasor diagram: Stand-alone cavities

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Figure 12

Dynamic pressure phase: 0deg row and X-direction excitation

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Figure 13

Dynamic force density and pressure phase: Inactive plenums

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Figure 14

Rotordyanmic force coefficients: Dynamic pressure response method, nonrotating

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Figure 15

Rotordynamic force coefficients: Mechanical impedance method, 15,200rpm




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