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Research Papers

Application of Film Cooling to an Unshrouded High-Pressure Turbine Casing

[+] Author and Article Information
Matthew Collins

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: matthew.collins@eng.ox.ac.uk

Kamaljit Chana

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: kam.chana@eng.ox.ac.uk

Thomas Povey

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: thomas.povey@eng.ox.ac.uk

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 7, 2016; final manuscript received November 2, 2016; published online February 7, 2017. Editor: Kenneth Hall.

J. Turbomach 139(6), 061010 (Feb 07, 2017) (12 pages) Paper No: TURBO-16-1231; doi: 10.1115/1.4035276 History: Received September 07, 2016; Revised November 02, 2016

In this paper, we describe the design, modeling, and experimental testing of a film cooling scheme employed on an unshrouded high-pressure (HP) rotor casing. The casing region has high thermal loads at both low and high frequency, with the flow being dominated by the potential field of the rotor and over-tip leakage flows. Increasingly high turbine entry temperatures necessitate internal and film cooling of the casing to ensure satisfactory service life and performance. There are, however, very few published studies presenting computational fluid dynamics (CFD) and experimental data for cooled rotor casings. Experimental testing was performed on a film-cooled rotor casing in the Oxford Turbine Research Facility (OTRF)—a rotating transonic facility of engine scale. Unsteady CFD of an HP rotor blade row with a film-cooled casing was undertaken, uniquely with a domain utilizing a sliding interface in the tip gap. A high density array of thin film heat flux gauges (TFHFGs) was used to obtain time-resolved and time-mean results of adiabatic wall temperature and film cooling effectiveness on the film-cooled rotor casing between −30% and +125% rotor tip axial chord. Results are compared to CFD predictions, and mechanisms for interaction of the coolant with the rotor tip are proposed and discussed. Acoustic effects within casing coolant holes due to the passing of the rotor are demonstrated on a 3D CFD geometry, supporting conclusions drawn in earlier work by the authors on the importance of this effect in a casing film cooling system.

Copyright © 2017 by ASME
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References

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Figures

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Fig. 1

Rotor mesh (left) and mesh of cooling hole on casing local to rotor tip (right)

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Fig. 2

Geometry A time instantaneous η′

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Fig. 3

Geometry A time-averaged η′

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Fig. 4

Geometry A time instantaneous isosurfaces of nondimensional temperature (Θ′=0.25). View of tip leakage and passage vortices.

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Fig. 5

Geometry A time instantaneous isosurfaces of nondimensional temperature (Θ′=0.25). View of casing surface from hub.

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Fig. 6

Geometry B time instantaneous η′

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Fig. 7

Geometry B time-averaged η′

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Fig. 8

Over-tip leakage flow relative to the rotor over a thick blade

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Fig. 9

Plot of unsteady m˙C across exit plane of holes located at 13% CAX with p0c/pe¯=1.14 (a) and 72% CAX with p0c/pe¯=1.51 (b)

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Fig. 10

Schematic of OTRF

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Fig. 11

Installed cooling module located in aluminum cassette (rotor not present)

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Fig. 12

Cooling module internal volumes

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Fig. 13

Cooling module incorporating coolant feed system, water cooling loop, 96 TFHFGs, nine thermocouples, four pressure tappings, and one pressure transducer

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Fig. 14

Cooling module flow calibration rig schematic

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Fig. 15

Instrumented casing region with 96 TFHFGs

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Fig. 16

Schematic of wall heating/cooling hardware

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Fig. 17

Time-averaged plots of TAW (a) and Nu (b) on cooled casing surface with uncooled data presented by Collins et al. [9]

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Fig. 18

Time-averaged plot of η′ obtained by comparing with uncooled experimental results

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Fig. 19

Schematic illustrating unsteady data processing to extract TAW and HTC as functions of rotor pitch

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Fig. 20

Time-resolved experimental measurements of rotor casing unsteady heat flux (a) and TAW (b) with gauge locations relative to cooling holes marked

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Fig. 21

Time-resolved experimental measurements of η′ with gauge locations relative to cooling holes marked

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Fig. 22

Time-resolved experimental measurements of uncooled rotor casing unsteady heat flux (a), TAW (b), and Nu (c) [9]

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Fig. 23

Time-resolved TAW (a) and η′ (b) extracted from geometry B CFD presented earlier

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Fig. 24

A 95% confidence interval of TAW as a proportion of measured value obtained from regression

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