Research Papers: Gas Turbines: Structures and Dynamics

Leakage Degradation of Straight Labyrinth Seal Due to Wear of Round Tooth Tip and Acute Trapezoidal Rub-Groove

[+] Author and Article Information
Yahya Dogu

Mechanical Engineering Department,
Kirikkale University,
Kirikkale 71450, Turkey
e-mail: yahya.dogu@hotmail.com

Mustafa C. Sertçakan

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: mustafacem.sertcakan@tei.com.tr

Koray Gezer

Mechanical Engineering Department,
Kirikkale University,
Kirikkale 71450, Turkey
e-mail: koraygezer90@gmail.com

Mustafa Kocagül

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: mustafa.kocagul@tei.com.tr

Ercan Arıcan

TUSAS Engine Industries, Inc. (TEI),
Eskisehir 26003, Turkey
e-mail: ercan.arican@tei.com.tr

Murat S. Ozmusul

Pro Solutions USA LLC,
453 Kinns Road,
Clifton Park, NY 12065
e-mail: ozmusul@prousa.us

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 9, 2016; final manuscript received December 15, 2016; published online March 7, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(7), 072506 (Mar 07, 2017) (12 pages) Paper No: GTP-16-1399; doi: 10.1115/1.4035657 History: Received August 09, 2016; Revised December 15, 2016

In this paper, labyrinth seal leakage is numerically quantified for an acute trapezoidal rub-groove accompanied with a rounded tooth, as a function of rub-groove sizes and tooth-groove axial positions. Analyses parameters include clearance, pressure ratio, number of teeth, and rotor speed. Labyrinth seals wear during engine transients. Radial incursion and axial movement of the rotor–stator pair cause the labyrinth teeth to rub against the unworn stator surface. The labyrinth teeth and/or stator wear depending on their material hardness. Wear damage in the form of material loss or deformation permanently increases seal clearance, and thus, leakage. This leakage is known to be dependent on the shape and geometry of the worn tooth and the stator rub groove. There are two types of reported tooth tip wear. These can be approximated as a mushroom shape and a round shape. The stator rub-groove shapes can be approximately simulated in five forms: rectangle, trapezoid (isosceles and acute), triangle, and ellipse. In this paper, the acute trapezoidal rub-groove shape is specifically chosen, since it is the most similar to the most commonly observed rub-groove form. The tooth tip is considered to be rounded, because the tooth tip wears smoothly and a round shape forms during rub-groove formation. To compare the unworn tooth, the flat stator is also analyzed as a reference case. All analyzed parameters for geometric dimensions (groove width, depth, wall angle, and tooth-groove axial position) and operating conditions (flow direction, clearance, pressure ratio, number of teeth, and rotor speed) are analyzed in their practical ranges. Computational fluid dynamics (CFD) analyses are carried out by employing a compressible turbulent flow solver in a 2D axisymmetrical coordinate system. CFD analyses show that the rounded tooth leaks more than an unworn sharp-edged tooth, due to the formation of a smooth and streamlined flow around the rounded geometry. This smooth flow yields less flow separation, flow disturbance, and less of vena contracta effect. The geometric dimensions of the acute trapezoidal rub-groove (width, depth, wall angle) significantly affect leakage. The effects of clearance, pressure ratio, number of teeth, and rotor speed on the leakage are also quantified. Analyses results are separately evaluated for each parameter.

Copyright © 2017 by ASME
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Chupp, R. E. , Hendricks, R. C. , Lattime, S. B. , and Steinetz, B. M. , 2006, “ Sealing in Turbomachinery,” Report No. NASA-TM 2006-214341.
Ghasripoor, F. , Turnquist, N. A. , and Kowalczyk, M. , 2004, “ Wear Prediction of Strip Seals Through Conductance,” ASME Paper No. GT2004-53297.
Neef, M. , Sulda, E. , Sürken, N. , and Walkenhorst, J. , 2006, “ Design Features and Performance Details of Brush Seals for Turbine Applications,” ASME Paper No. GT2006-90404.
Wilson, S. , 2007, “ Ensuring Tight Seals,” Vol. 2, Sulzer Technical Review, 89(2), pp. 23–25.
Herrmann, N. , Dullenkopf, K. , and Bauer, H.-J. , 2013, “ Flexible Seal Strip Design for Advanced Labyrinth Seals in Turbines,” ASME Paper No: GT2013-95424.
Combined Cycle Journal, 2014, CCJ ONsite, Las Vegas, NV, accessed Oct. 20 2014, http://www.ccj-online.com/501fg-users-benefit-from-presentations-by-non-oem-equipmentservices-providers-1-of-2/
Pychynski, T. , Höfler, C. , and Bauer, H.-J. , 2016, “ Experimental Study on the Friction Contact Between a Labyrinth Seal Fin and a Honeycomb Stator,” ASME J. Eng. Gas Turbines Power, 138(6), p. 062501. [CrossRef]
Zimmerman, H. , Kammerer, A. , and Wolff, K. H. , 1994, “ Performance of Worn Labyrinth Seals,” ASME Paper No. 94-GT-131.
Bill, R. C. , and Shiembob, L. T. , 1977, “ Friction and Wear of Sintered Fibermetal Abradable Seal Materials,” J. Lubrication Tech., 99(4), pp. 421–427. [CrossRef]
Chougule, H. H. , Ramerth, D. , Ramchandran, D. , and Kandala, R. , 2006, “ Numerical Investigation of Worn Labyrinth Seals,” ASME Paper No. GT2006-90690.
Delebarre, C. , Wagner, V. , Paris, J. Y. , Dessein, G. , Denape, J. , and Gurt-Santanach, J. , 2014, “ An Experimental Study of The High Speed Interaction Between a Labyrinth Seal and an Abradable Coating in a Turbo-Engine Application,” Wear, 316(1–2), pp. 109–118. [CrossRef]
Xu, J. , 2006, “ Effects of Operating Damage of Labyrinth Seal on Seal Leakage and Wheelspace Hot Gas Ingress,” Ph.D. thesis, Texas A&M University, College Station, TX.
Yan, X. , Lijie, L. , Li, J. , and Zhenping, F. , 2014, “ Effect of Bending and Mushrooming Damages on Heat Transfer Characteristic in Labyrinth Seals,” ASME J. Eng. Gas Turbines Power, 136(4), p. 041901. [CrossRef]
Dogu, Y. , Sertçakan, M. C. , Bahar, A. S. , Pişkin, A. , Arıcan, E. , and Kocagül, M. , 2016, “ Computational Fluid Dynamics Investigation of Labyrinth Seal Leakage Performance Depending on Mushroom-Shaped Tooth Wear,” ASME J. Eng. Gas Turbines Power, 138(3), p. 032503. [CrossRef]
Keller, C. , 1937, “ Flow Through Labyrinth Glands,” Power Plant Eng., 41(4), pp. 243–245.
ESDU, 2009, “ Labyrinth Seal Flow,” The Institution of Mechanical Engineers, Bracknell, UK, Standard No. ESDU 09004.
Rhode, D. L. , and Adams, R. G. , 2001, “ Computed Effect of Rub-Groove Size on Stepped Labyrinth Seal Performance,” Tribol. Trans., 44(4), pp. 523–532. [CrossRef]
Rhode, D. L. , and Adams, R. G. , 2004, “ Rub-Groove Width and Depth Effects on Flow Predictions for Straight-Through Labyrinth Seals,” ASME J. Tribol., 126(4), pp. 781–787. [CrossRef]
Xu, J. , Ambrosia, M. S. , and Rhode, D. L. , 2005, “ Effect of Rub-Groove Wall Angle on the Leakage of Abradable Stepped Labyrinth Seals,” Tribol. Trans., 48(4), pp. 443–449. [CrossRef]
Pychynski, T. , Dullenkopf, K. , Bauer, H.-J. , and Mikut, R. , 2010, “ Modelling The Labyrinth Seal Discharge Coefficient Using Data Mining Methods,” ASME Paper No. GT2010-22661.
Wang, W. Z. , Liu, Y. Z. , Meng, G. , and Jiang, P. N. , 2010, “ Influence of Rub Groove on Rotordynamics Associated With Leakage Air Flow Through a Labyrinth Seal,” J. Mech. Sci. Tech., 24(8), pp. 1573–1581. [CrossRef]
Pandit, R. K. , and Innocenti, L. , 2013, “ Computational Analysis of Abradable Seal—Part 1,” ASME Paper No. GT2013-94085.
Rhode, D. L. , and Allen, B. F. , 1998, “ Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals,” ASME Paper No. 98-GT-506.
Rhode, D. L. , and Allen, B. F. , 2001, “ Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths,” ASME J. Eng. Gas Turbines Power, 123(3), pp. 604–611. [CrossRef]
Denecke, J. , Schramm, V. , Kim, V. , and Wittig, S. , 2003, “ Influence of Rub-Grooves on Labyrinth Seal Leakage,” ASME J. Turbomach., 125(2), pp. 387–393. [CrossRef]
Innocenti, L. , Recupero, S. , Pandit, R. K. , and Sheng, N. , 2013, “ Experimental Analysis of Abradable Labyrinth Seal Leakage With Simulated Groove—Part 2,” ASME Paper No. GT2013-95646.
Collins, D. , Teixeira, J. , and Crudgington, P. , 2008, “ The Degradation of Abradable Honeycomb Labyrinth Seal Performance Due to Wear,” Sealing Technol., 2008(8), pp. 7–10. [CrossRef]
Nayak, K. C. , and Dutta, P. , 2016, “ Effect of Rub-Grooves on Leakage and Windage Heating in Straight-Through Labyrinth Seals,” ASME J. Tribol., 138(2), p. 022201. [CrossRef]
Dogu, Y. , Sertçakan, M. C. , Gezer, K. , Arıcan, E. , Kocagül, M. , and Ozmusul, M. S. , 2016, “ Labyrinth Seal Leakage Degradation Due To Various Types of Wear,” ASME Paper No. GT2016-57944.
ANSYS, 2013, “ ANSYS Fluent User's Guide, Release 15,” Ansys, Inc., Canonsburg, PA.
Waschka, W. , Wittig, S. , and Kim, S. , 1992, “ Influence of High Rotational Speeds on the Heat Transfer and Discharge Coefficients in Labyrinth Seals,” ASME J. Turbomach., 114(2), pp. 462–468. [CrossRef]
Wittig, S. , Jacobsen, K. , Schelling, U. , and Kim, S. , 1988, “ Heat Transfer in Stepped Labyrinth Seal,” ASME J. Eng. Gas Turbines Power, 110(1), pp. 63–69. [CrossRef]


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Fig. 1

Photographs for shapes of tooth tip wear and rub-groove: (a) [8], (b) [2], (c) [3], (d) [4], (e) [5], (f) [6], (g) [7], (h) [9], (i) [8], (j) [10], (k) [4], and (l) [11]

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Fig. 2

Possible wear shapes for tooth and rub-groove

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Fig. 3

Geometry of round tooth and rub-groove

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Fig. 4

Representative labyrinth seal geometry and boundary conditions

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Fig. 5

Representative mesh generation

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Fig. 6

Test and CFD model comparisons (a) straight labyrinth seal without rub-groove and (b) stepped labyrinth seal with rub-groove

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Fig. 7

Flow pattern plots for unworn seal and worn tooth with groove: (a) nondimensional pressure contours, (b) Mach number contours, (c) velocity vectors, and (d) velocity vectors around first tooth

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Fig. 8

Nondimensional pressure change at midline of clearance

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Fig. 9

Leakage and discharge coefficient versus groove width

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Fig. 10

Leakage and discharge coefficient versus groove depth

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Fig. 11

Discharge coefficient versus tooth-groove axial position

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Fig. 12

Leakage and discharge coefficient versus groove wall angle at downstream side

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Fig. 13

Leakage and discharge coefficient for straight and reversed flow directions

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Fig. 14

Leakage and discharge coefficient versus tooth clearance

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Fig. 15

Leakage and discharge coefficient versus pressure ratio

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Fig. 16

(a) Leakage and discharge coefficient versus number of teeth and (b) percentage of leakage reduction for increment of number of teeth

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Fig. 17

Leakage and discharge coefficient versus rotor speed

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Fig. 18

Velocity vectors and Mach number around first tooth for n = 0 and 40 krpm

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Fig. 19

Nondimensional axial velocity at first tooth clearance region showing vena contracta effect for n = 0 and 40 krpm




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