Research Papers: Gas Turbines: Structures and Dynamics

Pressure Activated Leaf Seal Technology Readiness Testing

[+] Author and Article Information
Aaron Bowsher

Cross Manufacturing Company,
Hopton Park, London Road,
Devizes, Wiltshire SN10 2EU, UK
e-mail: aaron.bowsher@cross-devizes.co.uk

Peter Crudgington

Cross Manufacturing Company,
Hopton Park, London Road,
Devizes, Wiltshire SN10 2EU, UK
e-mail: pete.crudgington@cross-devizes.co.uk

Clayton M. Grondahl

29 Stony Brook Drive,
Rexford, NY 12148
e-mail: cmgtech@earthlink.net

James C. Dudley

11444 Brittany Woods Lane,
Cincinnati, OH 45249
e-mail: JimDudley@cinci.rr.com

Tracey Kirk

Cross Manufacturing Company,
Hopton Park, London Road,
Devizes, Wiltshire SN10 2EU, UK
e-mail: tracey.kirk@cross-devizes.com

Andrew Pawlak

Cross Manufacturing Company,
Hopton Park, London Road,
Devizes, Wiltshire SN10 2EU, UK
e-mail: andrew.pawlak@cross-devizes.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 22, 2014; final manuscript received August 22, 2014; published online December 9, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(6), 062503 (Jun 01, 2015) (10 pages) Paper No: GTP-14-1426; doi: 10.1115/1.4028678 History: Received July 22, 2014; Revised August 22, 2014; Online December 09, 2014

This paper continues the evaluation of pressure actuated leaf seals (PALSs) technology readiness for shaft and shroud sealing in power generation and aerospace applications. Seal designs tested are prototypical and constructed using processes appropriate for volume production. Results include both static and dynamic seal leakage measurements running against a 5.1 in. (130 mm) diameter smooth surface test rotor and another that simulates sealing against turbine blade shrouds. A further test was undertaken using a two-dimensional (2D) static rig that determined acoustic noise experienced during testing was attributed to leaves vibrating at their natural frequency as a result of interleaf gaps. The dynamic simulated shroud test includes steps, duplicating small discontinuities of adjacent shroud sealing surfaces and slots to inject air radially under the seal leaves as may occur between shrouds on blades with a high degree of reaction. Consistent seal performance over 15 h confirms suitability for turbine blade tip applications. Controlled deflection of PALS leaves with operating differential pressure is effective for startup rub avoidance in service as well as conformal wear-in sizing of leaf tips with the rotor. Tested leaf tip wear-in of approximately 0.010 in. (0.25 mm) against rotor disks without hard-face coating shows potential to eliminate seal misalignment and run-out contributions to operating seal clearance. PALS design features prevent further rubbing contact with the operating rotor after initial wear-in sizing, thereby sustaining a small effective seal clearance and prospects for long seal life. Measurements of rotor surface wear tracks from the wear-in process and endurance runs are included as well as rotor and leaf tip photos. Test results support the technology readiness of the PALS concept as a viable, robust, low leakage dynamic seal for select commercial application.

Copyright © 2015 by ASME
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Fig. 1

Pressure activated leaf assembly

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Fig. 2

PALS prototype seal section

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Fig. 3

Leaf tip detail, LP side

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Fig. 4

PALS 5.1 in. (130 mm) diameter test seal

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Fig. 5

PALS from sheet stock

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Fig. 6

Illustration of PALS in 5.1 in. (130 mm) test rig

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Fig. 7

Photos of PALS installation in the 5.1 in. (130 mm) test rig

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Fig. 8

PALS clearance with various static disk sizes

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Fig. 9

Test seal leaf tips

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Fig. 10

Leaf tip burr—post wear-in (view from bottom)

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Fig. 11

Leaf tip burr—post wear-in (view from top)

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Fig. 12

PALS dynamic test clearance during and after wear-in

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Fig. 13

PALS static cycling after wear-in

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Fig. 14

PALS hi-pressure dynamic cycling clearance

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Fig. 15

PALS interleaf leakage assessment

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Fig. 16

PALS post test closure analysis

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Fig. 17

2D leaf test rig design

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Fig. 18

2D leaf test rig photo

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Fig. 19

Sequence for testing in 2D leaf test rig

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Fig. 20

2D leaf clearance, varying leaf angle

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Fig. 21

Seal with intentionally damaged leaves

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Fig. 22

Intentionally damaged leaves, post testing

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Fig. 23

Damaged seal noise signal at 5 and 10 psi, respectively

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Fig. 24

Shrouded rotor test schematic with air flow path

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Fig. 25

Shrouded rotor test setup

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Fig. 26

Rotor slot and step detail, 12 places

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Fig. 27

Total effective clearance over the 15 h test with test breakdown intervals shown

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Fig. 28

Leaves at 0 h and 15 h of testing

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Fig. 29

Burr formation in both top and bottom leaves

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Fig. 30

Rotor wear track at 15 h of testing

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Fig. 31

Rotor wear traces after 1 h and 15 h of testing

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Fig. 32

Total effective clearance running reverse rotation at varying speeds

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Fig. 33

Static leakage results pre- and post-testing




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