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Research Papers

Measurements of Secondary Losses in a Turbine Cascade With the Implementation of Nonaxisymmetric Endwall Contouring

[+] Author and Article Information
D. C. Knezevici

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON, K1S 5B6, Canadadknezevi@connect.carleton.ca

S. A. Sjolander

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON, K1S 5B6, Canadassjoland@mae.carleton.ca

T. J. Praisner

Turbine Aerodynamics, United Technologies,  Pratt & Whitney Aircraft, 400 Main Street, MS 169-29, East Hartford, CT 06108thomas.praisner@pw.utc.com

E. Allen-Bradley

Turbine Aerodynamics, United Technologies,  Pratt & Whitney Aircraft, 400 Main Street, MS 169-29, East Hartford, CT 06108eunice.allen-bradley@pw.utc.com

E. A. Grover

Turbine Aerodynamics, United Technologies,  Pratt & Whitney Aircraft, 400 Main Street, MS 169-29, East Hartford, CT 06108eric.grover@pw.utc.com

J. Turbomach 132(1), 011013 (Sep 17, 2009) (10 pages) doi:10.1115/1.3072520 History: Received September 08, 2008; Revised October 29, 2008; Published September 17, 2009

An approach to endwall contouring has been developed with the goal of reducing secondary losses in highly loaded axial flow turbines. The present paper describes an experimental assessment of the performance of the contouring approach implemented in a low-speed linear cascade test facility. The study examines the secondary flows of a cascade composed of Pratt & Whitney PAKB airfoils. This airfoil has been used extensively in low-pressure turbine research, and the present work adds intrapassage pressure and velocity measurements to the existing database. The cascade was tested at design incidence and at an inlet Reynolds number of 126,000 based on inlet midspan velocity and axial chord. Quantitative results include seven-hole pneumatic probe pressure measurements downstream of the cascade to assess blade row losses and detailed seven-hole probe measurements within the blade passage to track the progression of flow structures. Qualitative results take the form of oil surface flow visualization on the endwall and blade suction surface. The application of endwall contouring resulted in lower secondary losses and a reduction in secondary kinetic energy associated with pitchwise flow near the endwall and spanwise flow up the suction surface within the blade passage. The mechanism of loss reduction is discussed in regard to the reduction in secondary kinetic energy.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Linear cascade test section

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Figure 2

Isometric view of profiled endwall

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Figure 6

(a) Endwall and (b) suction-surface oil surface flow visualization for the contoured endwall

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Figure 13

Pitchwise mass-averaged results for the 140% Bx measurement plane: (a) total pressure loss coefficient, (b) outlet flow angle, and (c) secondary kinetic energy coefficient

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Figure 12

Secondary velocity vectors with flood of streamwise vorticity coefficient (Cωs) and ((b) and (d)) line contours of total pressure loss coefficient (CPo) with flood of secondary kinetic energy coefficient (CSKE) at 140% axial cord

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Figure 11

Secondary velocity vectors with flood of streamwise vorticity coefficient (Cωs) and ((b) and (d)) line contours of total pressure loss coefficient (CPo) with flood of secondary kinetic energy coefficient (CSKE) at the trailing edge plane

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Figure 8

Secondary velocity vectors with flood of streamwise vorticity coefficient (Cωs) and ((b) and (d)) line contours of total pressure loss coefficient (CPo) with flood of secondary kinetic energy coefficient (CSKE) at 63% axial cord

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Figure 7

(a) Line contours of total pressure loss coefficient superimposed with flood of streamwise vorticity and (b) interpreted vortex structure at the trailing edge plane (1.00Bx)

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Figure 5

(a) Endwall and (b) suction-surface oil surface flow visualization for the planar endwall

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Figure 4

Loading distribution measured by Mahallati (13)

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Figure 3

Spanwise variation in total pressure coefficient as measured with a Pitot probe 1.2Bx upstream of the leading edge at y/s=0.5

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Figure 10

Secondary velocity vectors with flood of streamwise vorticity coefficient (Cωs) and ((b) and (d)) line contours of total pressure loss coefficient (CPo) with flood of secondary kinetic energy coefficient (CSKE) at 80% axial cord

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Figure 9

Secondary velocity vectors with flood of streamwise vorticity coefficient (Cωs) and ((b) and (d)) line contours of total pressure loss coefficient (CPo) with flood of secondary kinetic energy coefficient (CSKE) at 71% axial cord

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