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RESEARCH PAPERS

Effects of Inlet Ramp Surfaces on the Aerodynamic Behavior of Bleed Hole and Bleed Slot Off-Take Configurations

[+] 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 Department of Mechanical Engineering, Imperial College, London SW7 2AZ, UK

J. Turbomach 129(4), 659-668 (Dec 21, 2006) (10 pages) doi:10.1115/1.2752192 History: Received December 07, 2006; Revised December 21, 2006

Bleed off-take air pressure and the interaction of the off-take with the primary flow through the blade passage is determined by: (1) the location of the bleed off-take at the endwall relative to the blade passage; (2) the bleed flow rate; and (3) the off-take geometry. In the companion paper (Leishman, 2007, ASME J. Turbomach., 129, pp. 645–658) the effect of bleed rate and endwall location was investigated using a circular hole bleed off-take configuration; the circular hole was tested at three endwall locations and for bleed flow rates between 0% and 9% of the primary (core) flow through the blade passage. The effects of bleed off-take geometry are presented in this paper by comparing the aerodynamic behavior of a number of generic bleed off-take configurations. Using results from low-speed cascade experiments and three-dimensional numerical calculations, the off-take configurations are compared with respect to the requirement to maximize bleed off-take air pressure and minimize loss generated within the blade passage. The off-take geometry, and especially the introduction of contoured inlet ramp surfaces to guide flow into the off-take for high bleed pressure, has a strong effect on its aerodynamic behavior because it determines the extent to which flow within the off-take is coupled to the primary flow through the blade passage. In this paper, the off-take configurations that give the highest bleed pressure generally cause the highest levels of loss in the blade passage.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Near pressure-surface bleed hole with ramped inlet surface (Case D), circular hole off-take (Case B)

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Figure 2

Measured bleed characteristics—Case D and circular hole (Case B)

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Figure 3

Case D: near pressure-surface hole with inlet ramp surface—measured contours of stagnation pressure loss (minimum contour 0.1, increment 0.1)

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Figure 4

Case D: endwall flow pattern at high bleed rate

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Figure 5

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

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Figure 6

Case E: downstream axisymmetric slot

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Figure 7

Case E: axisymmetric slot—measured contours of stagnation pressure loss (minimum Yp contour 0.1; contour increment 0.1)

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Figure 8

Case E: calculated contours of radial velocity inside the slot—8% bleed rate

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Figure 9

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

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Figure 10

Case E: bleed characteristic for downstream axisymmetric slots with inlet-edge fillet radius (R)

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Figure 11

Case E: axisymmetric slot (R∕D=0.58)—measured contours of stagnation pressure loss, Yp (minimum contour 0.1, increment 0.1)

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Figure 12

Case F: full-pitch ramped bleed slot

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Figure 13

Bleed characteristics

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Figure 14

Case F: full-pitch ramped bleed slot—measured contours of stagnation pressure loss (minimum contour 0.1, increment 0.1)

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Figure 15

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

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Figure 16

Case F: measured (exp) and calculated (CFD) exit profiles—(a) stagnation pressure loss; and (b) pitchwise flow angle

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Figure 17

Case F: calculated contours of radial velocity within slot—(a) zero bleed; (b) 4.0% bleed, and (c) 8.6% bleed

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