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Research Papers

The Effect of Leading-Edge Geometry on Wake Interactions in Compressors

[+] Author and Article Information
Andrew P. S. Wheeler2

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, United Kingdoma.wheeler@qmul.ac.uk

Alessandro Sofia3

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, United Kingdom

Robert J. Miller

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, United Kingdom

2

Corresponding author. Present address: School of Engineering and Materials Science, Queen Mary, University of London, UK.

3

Present address: ETH Zürich. This author performed his portion of this work at the Whittle Laboratory while he was an MS exchange student from ETH Zürich.

J. Turbomach 131(4), 041013 (Jul 06, 2009) (8 pages) doi:10.1115/1.3104617 History: Received October 13, 2008; Revised October 21, 2008; Published July 06, 2009

The effect of leading-edge geometry on the wake/boundary-layer interaction was studied in a low-speed single-stage HP compressor. Both a 3:1 elliptic and a circular leading edge were tested on a controlled diffusion aerofoil stator blade. Experiments were undertaken on the stator suction surface; these included hotwire boundary-layer traverses, surface hotfilm measurements, and high resolution leading-edge pressure measurements. Steady computational fluid dynamics (CFD) predictions were also performed to aid the interpretation of the results. The two leading-edge shapes gave rise to significantly different flows. For a blade with an elliptic leading edge (Blade A), the leading-edge boundary layer remained attached and laminar in the absence of wakes. The wake presence led to the formation of a thickened laminar boundary layer in which turbulent disturbances were observed to form. Measurements of the trailing-edge boundary layer indicated that the wake/leading-edge interaction for Blade A raised the suction-surface loss by 20%. For a blade with a circular leading edge (Blade B), the leading-edge boundary-layer exhibited a separation bubble, which was observed to reattach laminar in the absence of wakes. The presence of the wake moved the separation position forward while inducing a turbulent reattachment upstream of the leading-edge time-average reattachment position. This produced a region of very high momentum thickness at the leading edge. The suction-surface loss was found to be 38% higher for Blade B than for Blade A. Wake traverses downstream of the blades were used to determine the total profile loss of each blade. The profile loss of Blade B was measured to be 32% higher than that of Blade A.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The Deverson rig and working section

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Figure 2

Leading-edge geometries for Blades A and B

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Figure 3

The stator-blade pressure distribution for Blades A and B at midspan

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Figure 4

Time-average boundary-layer profile at 8.68% S0 for Blade A (δ/c=0.004)

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Figure 5

The time-average leading-edge pressure distributions for Blades A and B at midspan

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Figure 6

The leading-edge time-average boundary-layer integral parameters for Blade A suction surface (s/r=44s/S0)

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Figure 7

The leading-edge time-average boundary-layer integral parameters for Blade B suction surface (s/r=56s/S0)

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Figure 8

Variation in shape factor (H) with time at 8.68% S0 for Blades A and B

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Figure 9

Variation in momentum thickness (θ) with time at 8.68% S0 for Blades A and B

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Figure 10

Raw traces of quasi-shear-stress (τw) close to the leading edge for Blade A

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Figure 11

Ensemble-averaged quasi-shear-stress (τw) close to the leading edge for Blade B

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Figure 12

Raw traces of quasi-shear-stress (τw) close to the leading edge for Blade B

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Figure 13

S-t plot of normalized momentum thickness ((θ−θm)/θm) for Blade A

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Figure 14

S-t plot of normalized momentum thickness ((θ−θm)/θm) for Blade B

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Figure 15

Variation in energy thickness (ε) and momentum thickness (θ) at 97% S0 for Blades A and B

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Figure 16

Total-pressure wake profiles for Blades A and B at 0.3 axial chord downstream of the trailing edge

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