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Research Papers

Inverse Design of 3D Multistage Transonic Fans at Dual Operating Points

[+] Author and Article Information
James H. Page

Whittle Laboratory,
Department of Engineering,
University of Cambridge,
Cambridge CB3 0DY, UK
e-mail: jhp41@cam.ac.uk

Paul Hield

Fan Systems Engineering,
Rolls-Royce plc,
Filton, Bristol BS34 7QE, UK
e-mail: Paul.Hield@Rolls-Royce.com

Paul G. Tucker

Whittle Laboratory,
Department of Engineering,
University of Cambridge,
Cambridge CB3 0DY, UK
e-mail: pgt23@cam.ac.uk

The magnitude is initially estimated and subsequently updated to deliver the required streamline pressure ratio. The LE–TE distribution is specified by the designer.

The number of CFD iterations is for Turbostream and may vary for different solvers.

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received May 15, 2013; final manuscript received June 17, 2013; published online September 26, 2013. Editor: Ronald Bunker.

J. Turbomach 136(4), 041008 (Sep 26, 2013) (9 pages) Paper No: TURBO-13-1079; doi: 10.1115/1.4024884 History: Received May 15, 2013; Revised June 17, 2013

Semi-inverse design is the automatic recambering of an aerofoil during a computational fluid dynamics (CFD) calculation in order to achieve a target lift distribution while maintaining thickness, hence, “semi-inverse.” In this design method, the streamwise distribution of curvature is replaced by a streamwise distribution of lift. The authors have developed an inverse design code based on the method of Hield (2008, “Semi-Inverse Design Applied to an Eight Stage Transonic Axial Flow Compressor,” ASME Paper No. GT2008-50430), which can rapidly design three-dimensional fan blades in a multistage environment. The algorithm uses an inner loop to design to radially varying target lift distributions, an outer loop to achieve radial distributions of stage pressure ratio and exit flow angle, and a choked nozzle to set design mass flow. The code is easily wrapped around any CFD solver. In this paper, we describe a novel algorithm for designing simultaneously for specified performance at full speed and peak efficiency at part speed, without trade-offs between the targets at each of the two operating points. We also introduce a novel adaptive target lift distribution, which automatically develops discontinuous changes of calculated magnitude, based on the passage shock, eliminating erroneous lift demands in the shock vicinity and maintaining a smooth aerofoil.

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References

Figures

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Fig. 1

Two-stage fan geometry highlighting the camber line surface, used to manipulate the blade surface, and stacking axis

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Fig. 2

Illustration of the camber line preprocessing

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Fig. 3

Passage control volume relating (Δp)Target to (ΔrVθ)Target

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Fig. 4

Illustration of inverse design camber line modification process

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Fig. 5

3D mesh and block structure moving during inverse design

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Fig. 6

Rotor blade shape midspan before and after inverse design

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Fig. 7

Rotor blade lift midspan before and after inverse design

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Fig. 8

Stator blade shape midspan before and after inverse design

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Fig. 9

Stator blade lift midspan before and after inverse design

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Fig. 10

Illustration of inverse design characteristic

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Fig. 11

Flow diagram of inverse design wrapped around a fluid solver

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Fig. 12

Flow diagram of dual speed inverse design

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Fig. 13

Illustration of dual speed inverse design on a characteristic

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Fig. 14

Part speed calculation before inverse design: rotor PS (first and third rows) and stator SS (second and fourth rows)

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Fig. 15

Part speed calculation after inverse design

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Fig. 16

High speed calculation before inverse design: rotor PS (first and third rows) and stator SS (second and fourth rows)

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Fig. 17

High speed calculation after inverse design

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Fig. 18

High speed PR convergence history

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Fig. 19

High speed mass flow convergence history

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Fig. 20

High speed stage 1 radial exit total pressure

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Fig. 21

High speed stage 2 radial exit total pressure

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Fig. 22

High speed stage 1 radial exit flow angle

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Fig. 23

High speed stage 2 radial exit flow angle

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Fig. 24

Characteristic plot for 90% and 100% speeds

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Fig. 25

Efficiency plot for 90% and 100% speeds

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Fig. 26

Lift regions for shock well inside passage

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Fig. 27

Lift regions for shock at beginning of passage

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Fig. 28

Diagram of transonic lift distribution regions and SS shock jump calculation

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Fig. 29

Lift from CFD with target for a forward passage shock

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Fig. 30

Blade shape corresponding to forward passage shock lift distribution

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Fig. 31

Lift from CFD with target for a rearward passage shock

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Fig. 32

Blade shape corresponding to rearward passage shock lift distribution

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