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Research Papers: Other (Seals, Manufacturing)

Effect of Rub-Grooves on Leakage and Windage Heating in Straight-Through Labyrinth Seals

[+] Author and Article Information
Kali Charan Nayak

Department of Mechanical Engineering,
Indian Institute of Science,
Bangalore 560012, India
e-mail: kali_nayak@yahoo.co.in

Pradip Dutta

Department of Mechanical Engineering,
Indian Institute of Science,
Bangalore 560012, India

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 1, 2014; final manuscript received August 15, 2015; published online October 15, 2015. Assoc. Editor: Min Zou.

J. Tribol 138(2), 022201 (Oct 15, 2015) (11 pages) Paper No: TRIB-14-1247; doi: 10.1115/1.4031431 History: Received October 01, 2014; Revised August 15, 2015

Prediction of leakage flow and windage heating for labyrinth seals with honeycomb lands is critical in understanding gas turbine engine system performance and predicting its component life. There are several labyrinth seal configurations in use in gas turbines, and for each configuration, there are many geometric factors that can impact a seal's leakage and windage characteristics. One of the factors which has not been thoroughly investigated in previously published work is the presence of rub-grooves in the honeycomb land and its impact on seal performance. This paper describes the development of a numerical methodology aimed at studying this effect. Specifically, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the renormalization group (RNG) k-ε turbulence model. Using this model, a broad parametric study is conducted by varying honeycomb cell size and radial clearance for a four-tooth straight-through labyrinth seal with and without rub-grooves. The results show good agreement with available experimental data. They further indicate that presence of rub-grooves increases seal leakage and decreases windage heating. The absolute levels depend on the clearance and honeycomb cell size.

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Figures

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Fig. 1

Schematic of the problem of interest

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Fig. 2

No-rub and rubbed seal tooth tip configurations studied: (a) new seal (no-rub) and (b) worn seal (rubbed)

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Fig. 3

(a) Computational model with boundary conditions and (b) periodic 1/2-1-1/2 HC sector grid

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Fig. 4

Bypass flow at the seal tip through the honeycomb cells

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Fig. 5

Sensitivity of (a) grid resolution and (b) turbulence model on seal leakage

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Fig. 6

Seal leakage predictions at 0.5 mm clearance

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Fig. 7

Labyrinth seal leakage comparison for Collins experiment with smooth lands

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Fig. 8

Labyrinth seal leakage comparison for Collins experiment with 3.2 mm HCs

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Fig. 9

Seal leakage comparison: CFD, analytical correlation, and experiment

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Fig. 10

Windage heating comparison: CFD, analytical correlation, and experiment

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Fig. 11

Velocity vectors with swirl distribution: (a) CL = 0.75 mm, smooth, (b) CL = 0.75 mm, HC = 1.588 mm, and (c) CL = 0.25 mm, smooth

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Fig. 12

Pocket swirl comparison: CFD and analytical correlation and experiment

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Fig. 13

Effect of rub-grooves on flow bypassing through honeycomb cells at varied clearances

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Fig. 14

Flow field at the tooth tip for different clearances of the seal with HC = 3.2 mm and pressure ratio = 1.8: (a) CL = 0.25 mm, (b) CL = 0.5 mm, (c) CL = 1.0 mm, and (d) CL = 2.0 mm

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Fig. 15

Effect of rub-grooves on the seal tip flow field at 0.25 mm seal clearance: (a) no-rub, smooth, (b) rub, smooth, GD = 0.575 mm, (c) no-rub, HC = 3.2 mm, and (d) rub, HC = 3.2 mm, GD = 0.575 mm

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Fig. 16

Effect of rub-grooves on seal flow parameter for various honeycombs cell size at varied seal clearance

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Fig. 17

Effect of rub on seal flow parameter for various honeycomb cell sizes at varied clearance

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Fig. 18

Effect of rub-grooves on the seal tip flow field at different seal clearances with smooth lands: (a) CL = 0.25 mm, (b) CL = 1.0 mm, and (c) CL = 2.0 mm

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Fig. 19

Variation of pocket swirl with clearance for different HC sizes at rubbed and no-rub conditions. Pocket two swirl is taken for comparison.

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Fig. 20

Variation of windage number with clearance for different HC sizes at rubbed and no-rub conditions

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Fig. 21

Velocity vectors with swirl distribution for rub and no-rub conditions in 3.2 mm HC sizes at 0.25 mm seal clearance: (a) no-rub and (b) rub

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Fig. 22

Velocity vectors with axial velocity distribution for rub and no-rub conditions (HC = 3.2 mm): (a) CL = 0.25 mm, no-rub, (b) CL = 0.25 mm, rub, (c) CL = 1.0 mm, and (d) CL = 1.0 mm, rub

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