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Research Papers: Gas Turbines: Structures and Dynamics

Segmentation Effects on Brush Seal Leakage and Rotordynamic Coefficients

[+] Author and Article Information
Alexander O. Pugachev

Institute of Energy Systems,
Technische Universitaet Muenchen,
Garching 85748, Germany
e-mail: pugachev@tum.de

Manuel Gaszner

Institute of Energy Systems,
Technische Universitaet Muenchen,
Garching 85748, Germany
e-mail: gaszner@es.mw.tum.de

Christos Georgakis

Manager
CT Blades,
ALSTOM,
Rugby CV21 2NH, UK
e-mail: christos.georgakis@power.alstom.com

Paul Cooper

Steam Turbines Chief Engineers Office,
ALSTOM,
Rugby CV21 2NH, UK
e-mail: paul.cooper@power.alstom.com

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 25, 2015; final manuscript received July 17, 2015; published online September 22, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(3), 032501 (Sep 22, 2015) (9 pages) Paper No: GTP-15-1220; doi: 10.1115/1.4031386 History: Received June 25, 2015; Revised July 17, 2015

This paper studies the effect of brush seal segmentation on the seal performance characteristics. A brush–labyrinth sealing configuration arranged of one brush seal downstream and two labyrinth fins upstream is studied experimentally and theoretically. The studied brush seal is of welded design installed with zero cold radial clearance. The brush seal front and back rings as well as the bristle pack are segmented radially in a single plane using the electrical discharge machining (EDM) technique. The segmentation procedure results in loss of bristles at the site of the cuts altering the leakage flow structure in the seal and its performance characteristics. Two test rigs are used to obtain leakage, as well as rotordynamic stiffness and damping coefficients of the seal at different pressure ratios. The computational fluid dynamics (CFD)-based model is used to predict the seal performance and to study in detail local changes in the flow field due to the segmentation. A back-to-back comparison of the performance of nonsegmented and segmented brush seals as well as baseline labyrinth seal is provided. The obtained results demonstrate that the segmentation in general negatively affects the performance of the studied brush–labyrinth sealing configuration. However, the segmented brush seal shows increased direct damping coefficients.

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References

Figures

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Fig. 3

Schematics of the no-whirl test rig (left, drive is not shown) and the dynamic test rig (right)

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Fig. 2

Schematic of the segmented brush seal orientations

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Fig. 1

Studied sealing configuration

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Fig. 4

Circumferential pressure distribution for determination of local stiffness coefficients

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Fig. 5

Specific forces versus frequency for determination of global rotordynamic coefficients

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Fig. 6

Computational model of the studied sealing configuration

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Fig. 7

Experimental leakage of labyrinth and brush–labyrinth seals

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Fig. 11

Pressure distribution in the brush seal for two orientations of the segmentation plane

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Fig. 8

Experimental local aerodynamic stiffness coefficients versus pressure ratio

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Fig. 9

Experimental local aerodynamic stiffness coefficients versus eccentricity ratio

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Fig. 10

Experimental global stiffness and damping coefficients versus pressure ratio

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Fig. 12

Pressure distribution in cavities of brush–labyrinth seals

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Fig. 13

Predicted and experimental local stiffness coefficients versus pressure ratio

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Fig. 14

Predicted global aerodynamic stiffness and damping coefficients and experimental global stiffness and damping coefficients

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