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RESEARCH PAPERS

Effects of Bleed Rate and Endwall Location on the Aerodynamic Behavior of a Circular Hole Bleed Off-Take

[+] Author and Article Information
B. A. Leishman

 Rolls-Royce plc., Derby DE24 8BJ, UK

N. A. Cumpsty1

 Rolls-Royce plc., Derby DE24 8BJ, UK

J. D. Denton

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UK

1

Now at the Department of Mechanical Engineering, Imperial College, London SW7 2AZ, UK.

J. Turbomach 129(4), 645-658 (Dec 21, 2006) (14 pages) doi:10.1115/1.2752191 History: Received December 07, 2006; Revised December 21, 2006

In a jet engine bleed off-takes on the hub and casing endwalls, part way through the compressor, supply high-pressure air for cooling, sealing, de-icing, and aircraft cabin air applications; bleed also assists compressor operation at part-speed conditions. Two separate issues are of interest: the bleed off-take air pressure and the interaction of the bleed off-take with the primary flow through the blade passage. In this paper, the aerodynamic behavior is presented for a circular-hole bleed off-take at three endwall locations within a stationary cascade blade passage: at midpassage; near the blade pressure surface; and near the blade suction surface. Results from low-speed cascade experiments are complemented by three-dimensional numerical calculations using an unstructured mesh-based solver, in which the blade passage and bleed off-take geometry are fully modeled. The bleed off-take location and the magnitude of bleed rate influence the off-take air pressure and the interaction with the primary passage flow. For optimum design at zero and low bleed rates, off-takes near the blade pressure surface give the highest bleed air pressures and minimum loss in the blade passage. For minimum blade passage loss at higher bleed rates, however, it is necessary to take bleed near the blade suction surface. The paper discusses the causes for this pattern of behavior.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Circular bleed hole rotated to three different endwall locations

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Figure 2

Linear cascade rig

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Figure 3

Bleed characteristics for circular hole off-take at three endwall locations

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Figure 4

Case A: calculated contours of velocity—6.9% bleed rate

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Figure 5

Case A: circular hole at midpassage—measured contours of stagnation pressure loss, Yp (minimun contour 0.1, increment 0.1)

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Figure 6

Case A: measured exit profiles (a) stagnation pressure loss; and (b) pitchwise flow angle

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Figure 7

Calculated contours: (a) baseline: static pressure at 10% span; Case A: (b) static pressure at 10% span; and (c) radial velocity inside the hole (5% depth) for zero bleed rate

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Figure 8

Case A: endwall flow pattern at zero bleed rate: (a) surface flow visualization; and (b) calculated contours of axial velocity

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Figure 9

Case A: endwall flow pattern at high bleed rate: (a) surface flow visualization; and (b) calculated streamlines colored with Yp contours

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Figure 10

Case A: calculated streamlines showing vortex flow structure—9.3% bleed rate

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Figure 11

Case A: thick inlet boundary layer—measured contours of stagnation pressure loss, Yp (minimum contour 0.1, increment 0.1)

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Figure 12

Case B: circular hole near the pressure surface: measured contours of stagnation pressure loss, Yp (minimum contour 0.1, increment 0.1)

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Figure 13

Case B: measured exit profiles (a) stagnation pressure loss; and (b) pitchwise flow angle

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Figure 14

Case C: circular hole near the suction surface—measured contours of stagnation pressure loss, Yp (minimum contour 0.1, increment 0.1)

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Figure 15

Case C: measured exit profiles (a) stagnation pressure loss; and (b) pitchwise flow angle

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Figure 16

Measured blade pressure distributions at 10% span: (a) Case A: hole at midpassage; (b) Case B: hole near the pressure surface; and (c) Case C: hole near the suction surface

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Figure 17

Case A: calculated contours of static pressure at endwall for circular hole at midpassage configuration—9% bleed rate

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