Research Papers

The Impact of Geometric Variation on Compressor Two-Dimensional Incidence Range

[+] Author and Article Information
Martin N. Goodhand

Whittle Laboratory,
University of Cambridge,
Cambridge CB3 0D, UK
e-mail: mng24.cam@gmail.com

Robert J. Miller

Whittle Laboratory,
University of Cambridge,
Cambridge CB3 0D, UK
e-mail: rjm76@cam.ac.uk

Hang W. Lung

Rolls Royce plc,
Derby DE24 8BJ, UK
e-mail: hang.lung@rolls-royce.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 11, 2014; final manuscript received March 31, 2014; published online September 24, 2014. Editor: Ronald Bunker.

J. Turbomach 137(2), 021007 (Sep 24, 2014) (7 pages) Paper No: TURBO-14-1031; doi: 10.1115/1.4028355 History: Received March 11, 2014; Revised March 31, 2014

An important question for a designer is how, in the design process, to deal with the small geometric variations which result from either the manufacture process or in-service deterioration. For some blade designs geometric variations will have little or no effect on the performance of a row of blades, while in others their effects can be significant. This paper shows that blade designs which are most sensitive are those which are susceptible to a distinct switch in the fluid mechanisms responsible for limiting blade performance. To demonstrate this principle, the sensitivity of compressor 2D incidence range to manufacture variations is considered. Only one switch in mechanisms was observed, the onset of flow separation at the leading edge. This switch is only sensitive to geometric variations around the leading edge, 0–3% of the suction surface. The consequence for these manufacture variations was a 10% reduction in the blade's positive incidence range. For this switch, the boundary in the design space is best defined in terms of the blade pressure distribution. Blade designs where the acceleration exceeds a critical value just downstream of the leading edge are shown to be robust to geometric variation. Two historic designs, supercritical blades and blades with sharp leading edges, though superior in design intent, are shown to sit outside this robust region and thus, in practice, perform worse. The improved understanding of the robust, region of the design space is then used to design a blade capable of a robust, 5% increase in operating incidence range.

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Fig. 1

The limit of deterministic design for blades exposed to geometric variation

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Fig. 2

Two examples of design intent leading edge geometries and Mach number distributions at positive incidence

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Fig. 3

Weighting function used to impose manufacture variations over just the first 15% of the blade

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Fig. 4

Leading edges with imposed manufacture variations

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Fig. 5

Variation of profile loss with incidence for both leading edges with imposed manufacture variations

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Fig. 6

The effect of leading edge sharpness on positive and negative incidence range (MISES: M1 = 0.77, Re1 = 6.6 × 105)

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Fig. 7

Mach number distributions at positive incidence for blades with imposed manufacture variations

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Fig. 8

The effect of spike size on suction surface transition location at positive incidence (α = αdes + 5.8 deg). Conventional and sharp leading edges with imposed manufacture variations.

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Fig. 9

Sensitivity of the Mach number distribution to a large Hicks–Henne bump (MISES: α = αdes + 5.8 deg)

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Fig. 10

Sensitivity of suction surface Mach number to manufacture variations (MISES: α = αdes+5.8 deg)

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Fig. 11

Effect of flat leading edge on incidence range

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Fig. 12

Flat leading edge: velocity distribution and supersonic flow region

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Fig. 13

Sensitivity of negative incidence range to small amplitude Hicks–Henne bumps (conventional LE, rc0/tLE = 0.106)

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Fig. 14

Impact of increasing amplitude of modes determined from sensitivity analysis: (δ = 0—conventional LE, rc0/tLE = 0.106)

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Fig. 15

Effect of using sensitivity method to improve positive incidence range (conventional LE, rc0/tLE = 0.106); (a) sensitivity mode and (b) impact of imposing sensitivity mode




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