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TECHNICAL PAPERS

Combined Effects of Surface Trips and Unsteady Wakes on the Boundary Layer Development of an Ultra-High-Lift LP Turbine Blade

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

 Whittle Laboratory, Cambridge University, Madingley Road, Cambridge CB3 0DY, UK

J. Turbomach 127(3), 479-488 (Mar 01, 2004) (10 pages) doi:10.1115/1.1860571 History: Received October 01, 2003; Revised March 01, 2004

An experimental investigation of the combined effects of upstream unsteady wakes and surface trips on the boundary layer development on an ultra-high-lift low-pressure turbine blade, known as T106C, is described. Due to the large adverse pressure gradient, the incoming wakes are not strong enough to periodically suppress the large separation bubble on the smooth suction surface of the T106C blade. Therefore, the profile loss is not reduced as much as might be possible. The first part of this paper concerns the parametric study of the effect of surface trips on the profile losses to optimize the surface trip parameters. The parametric study included the effects of size, type, and location of the surface trips under unsteady flow conditions. The surface trips were straight cylindrical wires, straight rectangular steps, wavy rectangular steps, or wavy cylindrical wires. The second part studies the boundary layer development on the suction surface of the T106C linear cascade blade with and without the recommended surface trips to investigate the loss reduction mechanism. It is found that the selected surface trip does not induce transition immediately, but hastens the transition process in the separated shear layer underneath the wakes and between them. In this way, the combined effects of the surface trip and unsteady wakes further reduce the profile losses. This passive flow control method can be used over a relatively wide range of Reynolds numbers.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Flat plate test section with moving bars

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Figure 2

Geometry of wavy surface trips

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Figure 3

Schematic of T106C cascade with moving bars

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Figure 4

Flat plate surface pressure Cp distributions on smooth surface at Re=174,000

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Figure 5

Effects of trip height on losses under steady flow conditions at Tu=0.5%

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Figure 6

Effects of trip height on losses under unsteady flow conditions with f=0.83 and fr=0.57 at Tu=0.5%

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Figure 7

Effects of trip height on losses at Re=174,000 and Tu=0.5%

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Figure 8

Effects of surface trip on losses at Tu=3.5%

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Figure 9

Effects of trip shape on losses at Tu=0.5%

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Figure 10

Effects of trip location on losses at Tu=0.5%

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Figure 11

T106C linear cascade blade surface pressure Cp distributions at Re=174,000 and Tu=0.5%

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Figure 12

Total pressure loss coefficients of T106C linear cascade at Tu=0.5%

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Figure 13

Ensemble-averaged unsteady pressure traces at Re=174,000 and Tu=0.5% with f=0.83 and fr=0.57; (a) on smooth surface (b) with surface trip 5533

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Figure 14

Raw velocity traces at Re=174,000 and Tu=0.5% with f=0.83 and fr=0.57 at Yn=0.2mm

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Figure 15

Unsteady boundary layer integral parameters on smooth surface at Re=174,000 and Tu=0.5%

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Figure 16

Unsteady boundary layer integral parameters with straight step SS33 at Re=174,000 and Tu=0.5%

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