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Research Papers

Application of Endwall Contouring to Transonic Turbine Cascades: Experimental Measurements at Design Conditions

[+] Author and Article Information
Farzad Taremi

e-mail: ftaremi@connect.carleton.ca

Steen A. Sjolander

Chancellor’s Professor and Pratt and Whitney
Canada Research Fellow
e-mail: ssjoland@mae.carleton.ca
Department of Mechanical and Aerospace Engineering,
Carleton University,
Ottawa, ON, K1S 5B6, Canada

Thomas J. Praisner

Turbine Aerodynamics,
United Technologies, Pratt and Whitney,
East Hartford, CT 06118
e-mail: thomas.praisner@pw.utc.com

1Corresponding author.

Contributed by International Gas Turbine Institute of ASME for Publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 9, 2011; final manuscript received September 26, 2011; published online October 30, 2012. Editor: David Wisler.

J. Turbomach 135(1), 011031 (Oct 30, 2012) (12 pages) Paper No: TURBO-11-1179; doi: 10.1115/1.4006565 History: Received August 09, 2011; Revised October 04, 2011

An experimental investigation of the endwall flows in two high-turning turbine cascades was presented by Taremi et al. (2010, “Measurements of Endwall Flows in Transonic Linear Turbine Cascades: Part II—High Flow Turning,” ASME Conf. Proc., GT2010-22760, pp. 1343–1356). Endwall contouring was subsequently implemented in these cascades to control the secondary flows and reduce the total pressure losses. The current paper presents experimental results from these cascades to assess the effectiveness of endwall contouring in the transonic flow regime. The results include blade loadings, total pressure losses, streamwise vorticity and secondary kinetic energy distributions. In addition, surface flow visualization results are presented in order to interpret the endwall limiting streamlines within the blade passages. The flat-endwall and contoured-endwall cascades produce very similar midspan loading distributions and profile losses, but exhibit different secondary flows. The endwall surface flow visualization results indicate weaker interaction between the secondary flows and the blade suction surface boundary layers in the contoured cascades. Overall, the implementation of endwall contouring results in smaller and less intense vortical structures, and the reduction of the associated secondary kinetic energy (SKE) and exit flow angle variations. However, the mass-averaged losses at the main measurement plane, located 40% axial chord lengths downstream of the cascade (1.4CX), do not corroborate the numerically predicted improvements for the contoured cascades. This is in part attributed to slower mixing rates of the secondary flows in the compressible flow regime. The mass-averaged results at 2.0CX, on the other hand, show smaller losses for the contoured configurations associated with smaller SKE dissipation downstream of the cascades. Accordingly, the mixed-out row losses also show improvements for the contoured cascades.

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Figures

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Fig. 1

Endwall contouring features

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Fig. 2

CFD predictions: (a) normalized pitch-averaged total pressure loss coefficients and (b) exit flow angles

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Fig. 3

Pratt and Whitney Canada High-Speed Aerodynamics Laboratory

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Fig. 4

Turbine cascade flow features

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Fig. 5

Airfoil isentropic Mach number distributions

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Fig. 6

Endwall surface flow visualization results: (a) SL1F, (b) SL1C, (c) SL2F and (d) SL2C

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Fig. 7

(a) Streamwise vorticity coefficients and (b) pitch-averaged exit flow angles at 1.4CX

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Fig. 8

(a) CSKE and secondary velocities, and (b) pitch-averaged CSKE at 1.4CX

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Fig. 9

(a) CSKE and secondary velocities, and (b) pitch-averaged CSKE at 2.0CX

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Fig. 10

Normalized pitch-averaged energy loss coefficients at (a) 1.4CX and (b) 2.0CX

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