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Research Papers

The Impact of Real Geometries on Three-Dimensional Separations in Compressors

[+] Author and Article Information
Martin N. Goodhand

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UKmng24@cam.ac.uk

Robert J. Miller

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

J. Turbomach. 134(2), 021007 (Jun 22, 2011) (8 pages) doi:10.1115/1.4002990 History: Received June 28, 2010; Revised July 12, 2010; Published June 22, 2011; Online June 22, 2011

This paper considers the effect of small variations in leading edge geometry, leading edge roughness, leading edge fillet, and blade fillet geometry on the three-dimensional separations found in compressor blade rows. The detrimental effects of these separations have historically been predicted by correlations based on global flow parameters, such as blade loading, inlet boundary layer skew, etc., and thus ignoring small deviations such as those highlighted above. In this paper it is shown that this may not be the case and that certain, engine representative geometry deviations can have an effect equivalent to an increase in blade loading of 10%. Experiments were performed at the stator hub of a low-speed, single-stage compressor. The results show that any deviation which causes suction surface transition to move to the leading edge over the first 30% of span will cause a large growth in the size of the hub separation, doubling its impact on loss. The geometry deviations that caused this, and are thus of greatest concern to a designer, are changes in leading edge quality and roughness around the leading edge, which are characteristic of an eroded blade.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Three-dimensional separations: traditional view and scope of current investigation

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Figure 2

Schematic and operating conditions of compressor working section

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Figure 3

Experimental stagnation pressure loss coefficient, downstream of stators, ϕ=0.51, and rfill/c=4.8%

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Figure 4

Suction surface flow visualization at design conditions, ϕ=0.51, and rfill/c=4.8%

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Figure 5

Comparison of leading edge boundary layer state close to the hub, ϕ=0.51, s/s0=0.1, and rfill/c=4.8%

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Figure 6

CFD stagnation pressure loss coefficient, downstream of stators, ϕ=0.51, and rfill/c=4.8%

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Figure 7

Hub loss against flow coefficient, CFD, and experiments, rfill/c=4.8%

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Figure 8

Effect of a LE trip on the spanwise extent of the hub separation, ϕ=0.51, elliptical LE, and rfill/c=4.8%.

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Figure 9

Setup of smoke visualization experiment

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Figure 10

Smoke-visualization: growth with time of hub separation

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Figure 11

The effect of leading edge roughness height on the spanwise extent of the hub separation, ϕ=0.51, and rfill/c=4.8%

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Figure 12

The effect of surface roughness on an elliptical LE close to the hub. Rek=34, ϕ=0.51, and rfill/c=4.8%.

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Figure 13

Flow visualization showing the effect of a cut off fillet, elliptical leading edge, ϕ=0.51, and rfill/c=10%

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Figure 14

Effect of fillet radius on the spanwise extent of the hub separation, ϕ=0.51

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Figure 15

The effect of removing fillets on hub loss. Comparison with two leading edges, ϕ=0.51 and 0.45.

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Figure 16

The effect of small geometry changes on hub loss

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Figure 17

Computational stagnation pressure loss coefficients, high speed blade, and α1=49.6 (near stall)

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Figure 18

Endwall loss on high speed stator against incidence

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