Effects of Winglet Geometry on the Aerodynamic Performance of Tip Leakage Flow in a Turbine Cascade

[+] Author and Article Information
Chao Zhou

State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871, China

Howard Hodson

Whittle Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 0DY, 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 June 27, 2012; final manuscript received August 14, 2012; published online June 26, 2013. Editor: David Wisler.

J. Turbomach 135(5), 051009 (Jun 26, 2013) (10 pages) Paper No: TURBO-12-1082; doi: 10.1115/1.4007831 History: Received June 27, 2012; Revised August 14, 2012

Experimental and numerical methods were used to investigate the aerodynamic performance of a winglet tip in a linear cascade. A flat tip and a cavity tip were studied as baseline cases. The flow patterns over the three tips were studied. For the cavity tip and the winglet tip, vortices appear in the cavity and the gutter. These vortices reduce the discharge coefficient of the tip leakage flow. The purpose of using a winglet tip is to reduce the driving pressure difference. The pressure side winglet of the winglet geometry studied in this paper has little effect in reducing the driving pressure difference. It is found that the suction side winglet reduces the driving pressure difference of the tip leakage flow near the leading edge, but increases the driving pressure difference from midchord to the trailing edge. This is also used to explain the findings and discrepancies in other studies. Compared with the flat tip, the cavity tip and the winglet tip achieve a reduction of loss. The effects of the rounding of the pressure side edge of the tips were studied to simulate the effects of deterioration. As the size of the pressure side edge radius increases, the tip leakage mass flow rate and the loss increase. The improvement of the aerodynamic performance by using a winglet remains similar when comparing with a flat tip or a cavity tip with the same pressure side radius.

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Fig. 1

Winglet tips tested by Heyes

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Fig. 5

Midspan Cp distribution, CFD

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Fig. 4

Mesh of winglet tip, τ = 1.9%C

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Fig. 3

Geometry of cavity tip and winglet tip

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Fig. 6

Distributions of velocity at cut plane “A” in Fig. 7, V/V2, τ = 1.9%C, CFD

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Fig. 7

Cp distribution on endwall, winglet tip, τ = 1.9%C

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Fig. 8

Endwall Cp distribution at line “B,” winglet tip, τ = 1.9%C

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Fig. 9

Static pressure coefficient on suction side edge, CFD

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Fig. 14

Suction side winglet tips studied by Schabowski et al. [17]

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Fig. 12

Stagnation pressure coefficient at 45%Cx downstream trailing edge, τ = 1.9%C

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Fig. 13

Mixed-out tip leakage loss, τ = 1.9%C

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Fig. 10

Tip leakage mass flow rate per unit area that exits gap, CFD, τ = 1.9%C

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Fig. 11

Velocity distribution in middle of tip gap, winglet tip, V/V2, τ = 1.9%C, CFD

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Fig. 15

Suction side winglet studied in Camic [18]

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Fig. 16

Effects of size of tip gap, winglet tip, exp

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Fig. 17

Mixed-out tip leakage loss versus gap, exp

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Fig. 18

Effects of pressure side radius on loss, exp




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