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Research Papers

Application of a Novel Rotordynamic Identification Method for Annular Seals With Arbitrary Elliptical Orbits and Eccentricities

[+] Author and Article Information
Wanfu Zhang

Institute of Fluid Machinery and Engineering,
School of Energy and Power Engineering,
University of Shanghai for
Science and Technology,
No. 516 Jungong Road,
Shanghai 200093, China
e-mail: wfzhang@usst.edu.cn

Qianlei Gu

Institute of Fluid Machinery and Engineering,
School of Energy and Power Engineering,
University of Shanghai for
Science and Technology,
No. 516 Jungong Road,
Shanghai 200093, China
e-mail: 18321257669@163.com

Jiangang Yang

National Engineering Research Center
of Turbo-Generator Vibration,
Southeast University,
Sipailou 2#,
Nanjing, Jiangsu 210096, China
e-mail: jgyang@seu.edu.cn

Chun Li

Institute of Fluid Machinery and Engineering,
School of Energy and Power Engineering,
University of Shanghai for
Science and Technology,
No. 516 Jungong Road,
Shanghai 200093, China
e-mail: lichunusst@163.com

1Corresponding author.

Manuscript received February 8, 2019; final manuscript received June 16, 2019; published online July 12, 2019. Assoc. Editor: Harald Schoenenborn.

J. Eng. Gas Turbines Power 141(9), 091016 (Jul 12, 2019) (9 pages) Paper No: GTP-19-1051; doi: 10.1115/1.4044121 History: Received February 08, 2019; Revised June 16, 2019

The identification method using infinitesimal theory is proposed to predict rotordynamic coefficients of annular gas seals. The transient solution combined with moving grid method was unitized to obtain the fluid reaction force at a specific position under different whirling frequencies. The infinitesimal method is then applied to obtain the rotordynamic coefficients, which agrees well with published experimental results for both labyrinth seals and eccentric smooth annular seals. Particularly, the stability parameter of the effective damping coefficient can be solved precisely. Results show that the whirling frequency has little influence on direct damping coefficient, effective damping coefficient, and cross-coupled stiffness coefficient for the labyrinth seal. And the effective damping coefficients decrease as the eccentricity ratio increases. A higher eccentricity ratio tends to destabilize the seal system, especially at a low whirling frequency. Results also show that the fluid velocity in the maximum clearance in the seal leakage path is less than that in the minimum clearance. The inertial effect dominates the flow field. Then it results in higher pressure appearing in maximum clearances. The pressure difference aggravates the eccentricity of rotor and results in static instabilities of the seal system.

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Figures

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Fig. 1

Schematic diagram of quasi-steady state model

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Fig. 2

Rotordynamic model of the annular seals

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Fig. 3

Geometrical parameters of two types of the annular seals: (a) two-dimensional model of two types of annular seals and (b) local geometry of the labyrinth seal

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Fig. 5

Dynamic monitoring data: fluid forces (smooth annular seal)

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Fig. 6

Direct stiffness Kavg versus whirling frequency for the labyrinth seal

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Fig. 7

Direct damping Cavg versus whirling frequency for the labyrinth seal

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Fig. 8

Cross-coupled stiffness Kxy versus whirling frequency for the labyrinth seal

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Fig. 9

Effective damping Ceff versus whirling frequency for the labyrinth seal

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Fig. 10

Direct stiffness Kavg versus eccentricity ratio for the smooth annular seal

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Fig. 11

Direct damping Cavg versus eccentricity ratio for the smooth annular seal

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Fig. 12

Cross-coupled stiffness Kxy versus eccentricity ratio for the smooth annular seal

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Fig. 13

Effective damping Ceff versus eccentricity ratio for the labyrinth seal

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Fig. 14

Pressure difference in the labyrinth seal clearances

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Fig. 15

Velocity distribution in the labyrinth seal clearance

Tables

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