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Research Papers

The Aerothermal Performance of a Cooled Winglet Tip in a High Pressure Turbine Cascade

[+] Author and Article Information
Chao Zhou

State Key Laboratory for Turbulence and Complex Systems,
College of Engineering,
Peking University,
Beijing, 100871, China
e-mail: czhou@pku.edu.cn

Howard Hodson

Whittle Laboratory,
Department of Engineering,
University of Cambridge,
Cambridge, CB3 0FY, UK

Mark Stokes

Rolls-Royce plc,
Derby, DE24 8BJ, UK

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received November 12, 2011; final manuscript received November 29, 2011; published online March 25, 2013. Editor: David Wilser.

J. Turbomach 135(3), 031005 (Mar 25, 2013) (10 pages) Paper No: TURBO-11-1242; doi: 10.1115/1.4006611 History: Received November 12, 2011; Revised November 29, 2011

The aerothermal performance of a winglet tip with cooling holes on the tip and on the blade surface near the tip is reported in this paper. The investigation was based on a high pressure turbine cascade. Experimental and numerical methods were used. The effects of the coolant mass flow rate are also studied. Because the coolant injection partially blocks the tip leakage flow, more passage flow is turned by the blade. As a result, the coolant injection on the winglet tip reduces the deviation of the flow downstream of the cascade due to the tip leakage flow. However, the tip leakage loss increases slightly with the coolant mass flow ratio. Both the computational fluid dynamics tools and experiments using the Amonia–Diazo technique were used to determine the cooling effectiveness. On the blade pressure side surface, low cooling effectiveness appears around the holes due to the lack of the coolant from the cooling hole or the lift-off of the coolant from the blade surface when the coolant mass flow is high. The cooling effectiveness on the winglet tip is a combined effect of the coolant ejected from all the holes. On the top of the winglet tip, the average cooling effectiveness increases and the heat load decreases with increasing coolant mass flow. Due to its large area, the cooled winglet tip has a higher heat load than an uncooled flat tip at engine representative coolant mass flow ratio. Nevertheless, the heat flux rate per unit area of the winglet is much lower than that of an uncooled flat tip. The cycle analysis is carried out and the effects of relative tip-to-casing endwall motion are address.

Copyright © 2013 by ASME
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References

Figures

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Fig. 2

Geometry of cooled winglet tip

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Fig. 3

Mesh of cooled winglet tip, τ = 1.9% C

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Fig. 4

Midspan Cp distribution, CFD

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Fig. 5

Cp of internal cooling configuration, Mc,ER, τ = 1.9%C, CFD

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Fig. 6

Effects of coolant to flow field, τ = 1.9% C, 45% axial chord downstream cascade, exp

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Fig. 7

Tip leakage loss of cooled tip, τ = 1.9% C

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Fig. 8

Cooling effectiveness of cooled winglet tip, Mc,ER, τ = 1.9% C

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Fig. 9

Effects of coolant on blade surface, Mc,ER, CFD

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Fig. 10

Cooling effectiveness of cooled winglet tip, Mc,ER, τ = 1.9% C, CFD

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Fig. 11

cooling effectiveness of blade suction side, Mc,ER, τ = 1.9% C, CFD

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Fig. 12

Nusselt number of cooled winglet tip, Mc,ER, τ = 1.9% C, CFD

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Fig. 13

Effects of coolant mass flow ratio—cooling effectiveness, pressure side surface, τ = 1.9% C, CFD

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Fig. 14

Effects of coolant mass flow rate—cooling effectiveness, winglet tip, τ = 1.9% C, CFD

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Fig. 15

Effects of coolant mass flow ratio on thermal performance of cooled winglet tip, τ = 1.9% C, CFD

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Fig. 16

Effects of coolant mass flow ratio on engine core efficiency

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Fig. 17

Effects of endwall motion on the cooling effectiveness of winglet tip, CFD

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