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Research Papers

Compressor Leading Edge Spikes: A New Performance Criterion

[+] Author and Article Information
Martin N. Goodhand, Robert J. Miller

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

J. Turbomach 133(2), 021006 (Oct 20, 2010) (8 pages) doi:10.1115/1.4000567 History: Received July 20, 2009; Revised July 30, 2009; Published October 20, 2010; Online October 20, 2010

Compressor blades often have a small “spike” in the surface pressure distribution at the leading edge. This may result from blade erosion, manufacture defects, or compromises made in the original design process. This paper investigates the effect of these spikes on profile loss, and presents a criterion to ensure they are not detrimental to compressor performance. In the first part of the paper, two geometries of leading edge are tested. One has a small spike, typical of those found on modern compressors; the other has no spike, characteristic of an idealized leading edge. Testing was undertaken on the stator of a single-stage low speed compressor. The time resolved boundary layer was measured using a hot-wire microtraversing system. It is shown that the presence of the small spike changes the time resolved transition process on the suction surface, but that this results in no net increase in loss. In the second part of the paper, spike height is systematically changed using a range of leading edge geometries. It is shown that below a critical spike height, the profile loss is constant. If the critical spike height is exceeded, the leading edge separates and profile loss rises by 30%. Finally, a criterion is developed, based on the total diffusion across the spike. Three different leading edge design philosophies are investigated. It is shown that if the spike diffusion factor is kept below 0.1 over the blade’s incidence range, performance is unaffected by leading edge geometry.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of surface pressure distribution with enlargement of spike

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Figure 2

Thickness distribution of 3:1 elliptical LE

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Figure 3

Optimisation result in transformed space

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Figure 4

Comparison of incidence range, CFD, and surface pressure distributions, CFD, and experiment, iinlet=−2.9 deg

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Figure 5

Leading edge suction surface pressure distributions, CFD, and experimental showing Dspike

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Figure 6

Schematic of compressor working section

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Figure 7

Hotwire traverse locations

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Figure 8

Measured, time resolved, inlet incidence, and turbulence intensity

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Figure 9

Space-time diagram of suction surface intermittency and contours of calmed region, iinlet=−2.9 deg

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Figure 10

Space-time schematic of suction surface intermittency and extent of calmed region, iinlet=−2.9 deg

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Figure 11

Effect of inlet incidence on mean transition location (γ=0.5) within wakes and between wakes

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Figure 12

Measured energy thickness at peak suction, iinlet=−2.9 deg

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Figure 13

Measured trailing edge energy thickness, iinlet=−2.9 deg

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Figure 14

Effect of inlet incidence on the time averaged energy thickness at the trailing edge

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Figure 15

Space-time diagram of suction surface intermittency and contours of calmed region with a missing wake and elliptical leading edge, iinlet=−2.9 deg

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Figure 16

Energy thickness at s/s0=0.67 with a missing wake, elliptical leading edge, iinlet=−2.9 deg. Comparison of measured experimental data and CFD.

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Figure 17

Circular LE: space-time diagram of suction surface intermittency and separation bubble, iinlet=−2.9 deg

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Figure 18

Effect of spike diffusion factor on trailing edge energy thickness, iinlet=−2.9 deg

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Figure 19

Comparison of trailing edge energy thickness between blades with ellipse ratios 1.2 and 1.4 from Fig. 1, iinlet=−2.9 deg

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Figure 20

The effect of spike diffusion factor on suction surface transition location with three LE design philosophies

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Figure 21

Critical leading edges with different design philosophies, geometry, and leading edge surface pressure coefficient, iinlet=0.6 deg

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