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Research Papers

The Relative Performance of External Casing Impingement Cooling Arrangements for Thermal Control of Blade Tip Clearance

[+] Author and Article Information
Myeonggeun Choi

Department of Engineering Science,
University of Oxford,
Oxford OX1 3PJ, UK
e-mail: myeonggeun.choi@eng.ox.ac.uk

David M. Dyrda

Department of Engineering Science,
University of Oxford,
Oxford OX1 3PJ, UK

David R. H. Gillespie

Department of Engineering Science,
University of Oxford,
Oxford OX1 3PJ, UK
e-mail: david.gillespie@eng.ox.ac.uk

Orpheas Tapanlis

Department of Engineering Science,
University of Oxford,
Oxford OX1 3PJ, UK
e-mail: orpheas.tapanlis@gmail.com

Leo V. Lewis

Rolls-Royce plc,
P.O. Box 31,
Derby DE24 8BJ, UK
e-mail: leo.lewis@rolls-royce.com

1Current address: Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305-4035.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 31, 2015; final manuscript received October 21, 2015; published online December 15, 2015. Editor: Kenneth C. Hall.

J. Turbomach 138(3), 031005 (Dec 15, 2015) (12 pages) Paper No: TURBO-15-1174; doi: 10.1115/1.4031907 History: Received July 31, 2015; Revised October 21, 2015

As a key way of improving jet engine performance, a thermal tip clearance control system provides a robust means of manipulating the closure between the casing and the rotating blade tips, reducing undesirable tip leakage flows. This may be achieved using an impingement cooling scheme on the external casing. Such systems can be optimized to increase the contraction capability for a given casing cooling flow. Typically, this is achieved by changing the cooled area and local casing features, such as the external flanges or the external cooling geometry. This paper reports the effectiveness of a range of impingement cooling arrangements in typical engine casing closure system. The effects of jet-to-jet pitch, number of jets, and inline and staggered alignment of jets on an engine representative casing geometry are assessed through comparison of the convective heat transfer coefficient distributions as well as the thermal closure at the point of the casing liner attachment. The investigation is primarily numerical, however, a baseline case has been validated experimentally in tests using a transient liquid crystal technique. Steady numerical simulations using the realizable k–ε, k–ω SST, and EARSM turbulence models were conducted to understand the variation in the predicted local heat transfer coefficient distribution. A constant mass flow rate was used as a constraint at each engine condition, approximately corresponding to a constant feed pressure when the manifold exit area is constant. Sets of local heat transfer coefficient data generated using a consistent modeling approach were then used to create reduced order distributions of the local cooling. These were used in a thermomechanical model to predict the casing closure at engine representative operating conditions.

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References

Figures

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Fig. 1

High-pressure turbine casing configuration on (a) a typical large civil engine [11] and (b) a radial cross section through a typical manifold [9]

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Fig. 2

Computational domain for standalone casing external heat transfer prediction

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Fig. 3

Grid independent solution achieved

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Fig. 7

Local htc/htcref(=H2.peak.relizable kε.OP1) distributions with different turbulence models employed, OP1 condition

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Fig. 5

Schematic diagrams of the main components of the test rig

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Fig. 4

Idealized representation of casing FE model

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Fig. 8

Relative performance of spanwise-averaged htc/htcref(=H2.peak.span.relizable kε.OP1), at OP1 and OP2, for the changing turbulence model

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Fig. 6

Local htc/htcref(=H2.peak.relizable kε.OP1) distributions, experimental case Re = 6000, equivalent to OP1

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Fig. 9

Relative performance of (a) patch area averaged htc/htcref(=H2.patch.relizable kε.OP1) and (b) overall area averaged htc/htcref(=H2.avg.relizable kε.OP1) at OP1 and OP2 for the change in turbulence model employed

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Fig. 13

Local htc/htcref(=H2.peak.relizable kε.OP1) distributions, for different number of rows of jets, OP1

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Fig. 14

Spanwise-averaged htc/htcref(=H2.peak.span.relizable kε.OP1) distributions at OP1 and OP2, for different number of jet rows

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Fig. 10

Local htc/htcref(=H2.peak.relizable kε.OP1) distributions of the variation in jet-to-jet pitch at OP1

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Fig. 11

Spanwise-averaged htc/htcref(=H2.peak.span.relizable kε.OP1) distributions at OP1 and OP2, for the variation in jet-to-jet pitch

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Fig. 12

Relative performance of overall area averaged htc/htcref(=H2.avg.relizable kε.OP1) at OP1 and OP2

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Fig. 15

Local htc/htcref (=H2.peak.relizable kε.OP1) distributions of inline and staggered arrays of jets at OP1

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Fig. 16

Spanwise-averaged htc/htcref (=H2.peak.span.relizable kε.OP1) distributions at OP1 and OP2, for the inline and staggered arrays of jets

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Fig. 17

Predicted casing temperature (K) and thermal radial displacement (r, mm), baseline H2 cooling scheme at OP1 and OP2

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Fig. 18

Predicted casing temperature (K) and closure (mm) versus coolant mass flow rate, at liner attachment point for jet-to-jet pitch variation

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Fig. 19

Predicted casing temperature (K) and closure (mm) versus coolant mass flow rate, at liner attachment point, for the different number of jets

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Fig. 20

Predicted casing temperature (K) and closure (mm) versus coolant mass flow rate, at liner attachment point, for the inline and staggered arrays of jets

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Fig. 21

Relative performance of casing temperature drop at the liner attachment point by internal hooks, compared to baseline H2 scheme at OP1 and OP2

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Fig. 22

Relative performance of casing closure at the liner attachment point by internal hooks, compared to baseline H2 scheme at OP1 and OP2

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