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TECHNICAL PAPERS

Separation and Transition Control on an Aft-Loaded Ultra-High-Lift LP Turbine Blade at Low Reynolds Numbers: High-Speed Validation

[+] Author and Article Information
Maria Vera, Xue Feng Zhang, Howard Hodson

Whittle Laboratory,  University of Cambridge, UK

Neil Harvey

Compression Systems,  Rolls-Royce plc, Derby, UK

J. Turbomach 129(2), 340-347 (May 30, 2006) (8 pages) doi:10.1115/1.2437220 History: Received May 17, 2006; Revised May 30, 2006

This paper presents the second part of an investigation of the combined effects of unsteadiness and surface roughness on an aft-loaded ultra-high-lift low-pressure turbine (LPT) profile at low Reynolds numbers. The investigation has been performed using low- and high-speed cascade facilities. The low- and high-speed profiles have been designed to have the same normalized isentropic Mach number distribution. The low-speed results have been presented in the first part (Zhang, Vera, Hodson, and Harvey, 2006, ASME J. Turbomach., 128, pp. 517–527). The current paper examines the effect of different surface finishes on an aft-loaded ultra-high-lift LPT profile at Mach and Reynolds numbers representative of LPT engine conditions. The surface roughness values are presented along with the profile losses under steady and unsteady inflow conditions. The results show that the use of a rough surface finish can be used to reduce the profile loss. In addition, the results show that the same quantitative values of losses are obtained at high- and low-speed flow conditions. The latter proves the validity of the low-speed approach for ultra-high-lift profiles for the case of an exit Mach number of the order of 0.64. Hot-wire measurements were carried out to explain the effect of the surface finish on the wake-induced transition mechanism.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cross section of the high-speed bar rotating rig

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Figure 2

Characterisation of the surface finish

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Figure 3

Sf5 blade and close-up of the spanwise ribs

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Figure 4

Inviscid distribution of nondimensional isentropic Mach number around SF1 and SF6 profiles

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Figure 5

Nondimensional profile kinetic energy loss coefficient against Reynolds number; Ma3=0.64; manufacturing process M1

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Figure 6

Nondimensional profile kinetic energy loss coefficient against Reynolds number; Ma3=0.64; manufacturing process M2

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Figure 7

Contours of mean velocity (left) and ensemble averaged velocity (right) on Sf6 (top) and Sf5 (bottom): Ma3=0.64, Re3=9.0×104

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Figure 8

Contours of mean velocity (left) and ensemble averaged velocity (right) on Sf6 (top) and Sf1 (bottom): Ma3=0.64, Re3=1.45×105

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Figure 9

Contours of variance of the velocity at 79%S0, Sf1 (top) and Sf6 (bottom) blades: Ma3=0.64, Re3=1.45×105

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Figure 10

Contours of variance of the velocity at 79%S0 on the smooth surface at low speed: Re3=1.30×105

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