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Research Papers: Gas Turbines: Structures and Dynamics

A Generalized Prediction Method for Rotordynamic Coefficients of Annular Gas Seals

[+] Author and Article Information
Xin Yan

Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: xinyan@mail.xjtu.edu.cn

Kun He

MOE Key Laboratory of Thermo-Fluid
Science and Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: hekun@mail.xjtu.edu.cn

Jun Li

Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: junli@mail.xjtu.edu.cn

Zhenping Feng

Institute of Turbomachinery,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: zpfeng@mail.xjtu.edu.cn

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 18, 2014; final manuscript received February 8, 2015; published online March 17, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(9), 092506 (Sep 01, 2015) (12 pages) Paper No: GTP-14-1299; doi: 10.1115/1.4029883 History: Received June 18, 2014; Revised February 08, 2015; Online March 17, 2015

The improvement in rotordynamic performance of the annular gas seal requires efficient and accurate prediction methods of rotordynamic coefficients. Although the existed transient computational fluid dynamics (CFD) methods in published literature have excellent numerical accuracy, most of them face the challenge due to rotordynamic coefficients at every excitation frequency to be solved by a separate transient CFD prediction thus much time-consuming. In this paper, a generalized prediction method is proposed to address this difficulty. Based on the Laplace transform method, the solution procedures for the reaction force/motion equation of the annular gas seal are deduced. With the specified excitations (rotor motion), the rotordynamic coefficients at all excitation frequencies can be solved by only one or two transient CFD solutions. To verify the present generalized method, the rotordynamic coefficients of two typical hole-pattern seals are computed and compared to the available experimental data. The results show that the predicted rotordynamic coefficients are in good agreement with the experimental tests. Compared to the previous transient CFD methods, the computational time of the present generalized method is reduced significantly while the accuracy is still maintained.

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References

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Figures

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Fig. 1

Computational methodologies for the reaction force/motion equations. (a) Solution flow chart of Eq. (1). (b) Solution flow chart of Eq. (40).

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Fig. 2

Dimensions of the hole-pattern seals. (a) SDHP [13]. (b) LDHP (mm) [15].

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Fig. 3

Geometrical models for the hole-pattern seals. (a) SDHP seal [13]. (b) LDHP seal [15].

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Fig. 4

Computational meshes for the hole-pattern seals (close-up). (a) SDHP seal. (b) LDHP seal.

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Fig. 5

Motions of the hole-pattern seal

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Fig. 6

Fluid forces on the seal rotor. (a) SDHP. (b) LDHP.

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Fig. 7

Grid independent analysis for the SDHP seal. (a) Cross-coupled damping coefficient c. (b) Direct damping coefficient C. (c) Cross-coupled stiffness coefficient k. (d) Direct stiffness coefficient K. (e) Effective damping coefficient Ceff. (f) Effective stiffness coefficient Keff.

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Fig. 8

Grid independent analysis for the LDHP seal. (a) Cross-coupled damping coefficient c. (b) Direct damping coefficient C. (c) Cross-coupled stiffness coefficient k. (d) Direct stiffness coefficient K. (e) Effective damping coefficient Ceff. (f) Effective stiffness coefficient Keff.

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Fig. 9

Rotordynamic coefficients for the SDHP seal. (a) Cross-coupled damping coefficient c. (b) Direct damping coefficient C. (c) Cross-coupled stiffness coefficient k. (d) Direct stiffness coefficient K. (e) Effective damping coefficient Ceff. (f) Effective stiffness coefficient Keff.

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Fig. 10

Rotordynamic coefficients for the LDHP seal. (a) Cross-coupled damping coefficient c. (b) Direct damping coefficient C. (c) Cross-coupled stiffness coefficient k. (d) Direct stiffness coefficient K. (e) Effective damping coefficient Ceff. (f) Effective stiffness coefficient Keff.

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