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Gas Turbines: Structures and Dynamics

Investigations on the Rotordynamic Coefficients of Pocket Damper Seals Using the Multifrequency, One-Dimensional, Whirling Orbit Model and RANS Solutions

[+] Author and Article Information
Jun Li1

Institute of Turbomachinery,  Xi’an Jiaotong University, Xi’an 710049, Chinajunli@mail.xjtu.edu.cn

Zhigang Li

Institute of Turbomachinery,  Xi’an Jiaotong University, Xi’an 710049, Chinalzg-1126@stu.xjtu.edu.cn

Zhenping Feng

Institute of Turbomachinery,  Xi’an Jiaotong University, Xi’an 710049, China

1

Corresponding author.

J. Eng. Gas Turbines Power 134(10), 102510 (Aug 22, 2012) (11 pages) doi:10.1115/1.4007063 History: Received June 20, 2012; Revised June 23, 2012; Published August 22, 2012; Online August 22, 2012

The numerical approach using the multifrequency one-dimensional whirling orbit model and Reynolds-averaged Navier-Stokes (RANS) solution was proposed for prediction of rotordynamic coefficients of pocket damper seal (PDS). By conducting the multiple frequencies one-dimensional whirling orbit for rotor center as the excitation signal, the unsteady RANS solutions combined with mesh deformation method were utilized to calculate the transient response forces on the PDS rotor surface. Unlike the single frequency whirling orbit models which require a separate computation for each frequency, the multifrequency whirling orbit model yields results for multiple frequencies and therefore requires only one computation for different frequencies. The rotor motion signal and response force signal were transformed to the frequency domain using the fast fourier transform, then the eight rotordynamic coefficients of the PDS were determined at fourteen different vibration frequencies 20–300 Hz. The numerical results of rotordynamic coefficients of the PDS were in good agreement with experimental data. The accuracy and availability of the proposed method was demonstrated. The effects of vibration frequencies and pressure ratios on the rotordynamic coefficients of PDS were also investigated using the presented numerical method. The multifrequency one-dimensional whirling orbit model is a promising method for prediction of the rotordynamic coefficients of the PDS.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Geometries parameters of the eight-bladed PDS

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Figure 2

Computational model and mesh of the PDS

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Figure 3

Axial view of the rotor and PDS (concentric)

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Figure 4

One-dimensional whirling model (eccentric)

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Figure 5

Multifrequency vibration displacement of the rotor

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Figure 6

Dynamic monitoring data: rotor motion (x excitation, Π=0.326)

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Figure 7

Dynamic monitoring data: response force (x excitation, Π=0.326)

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Figure 8

Direct stiffness versus vibration frequency (Π=0.516,n=10200rpm)

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Figure 9

Direct damping versus vibration frequency (Π=0.516,n=10200rpm)

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Figure 10

Cross coupling stiffness versus vibration frequency (Π=0.516,n=10200rpm)

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Figure 11

Direct stiffness versus vibration frequency at different pressure ratios (n=10200rpm)

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Figure 12

Direct damping versus vibration frequency at different pressure ratios (n=10200rpm)

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Figure 13

Cross coupling stiffness and damping versus vibration frequency at different pressure ratios (n=10200rpm)

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Figure 14

Dynamic cavity pressure and rotor motion (x-direction excitation, n=10200rpm, Π=0.516)

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Figure 15

Static pressure contours and velocity distributions in the cross section through the middle of cavity 3 (x excitation, n=10200rpm, Π=0.516)

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Figure 16

Cavity level direct stiffness and damping (x excitation, n=10200rpm, Π=0.326)

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Figure 17

Cavity pressure phase (x excitation, n=10200rpm, Π=0.326)

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Figure 18

Seal leakage flow rate versus pressure ratio (n=10200rpm)

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