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Research Papers

Fan Root Aerodynamics for Large Bypass Gas Turbine Engines: Influence on the Engine Performance and 3D Design

[+] Author and Article Information
Giulio Zamboni

 Whittle Laboratory,Department of Engineering,University of Cambridge, Cambridge, CB3 0DY, UKgiuzam80@alice.it

Liping Xu

 Whittle Laboratory,Department of Engineering,University of Cambridge, Cambridge, CB3 0DY, UKlpx1@cam.ac.uk

J. Turbomach 134(6), 061017 (Sep 04, 2012) (11 pages) doi:10.1115/1.4006286 History: Received March 07, 2011; Revised June 12, 2011; Published September 04, 2012; Online September 04, 2012

The exit flow field of the fan root of large turbofan engines defines the inlet conditions to the core compressor. This in turn could have significant impact to the performance of the core compressor. This study is aimed to resolve two related issues concerning the impact of the fan root flow on the core compressor performance: to establish the effect of an increased loss at the inlet on the engine specific fuel consumption (SFC) and to assess the effect of the radial distribution of the fan root flow on the engine performance. With understanding of these issues, the geometric parameters and design details which can produce a more uniform core flow at the exit of the fan stage module can be identified. The fan root flow is analyzed with methods of different complexity and fidelity. A simple cycle analysis is used to assess the impact on engine SFC of a stagnation pressure deficit at the fan root; a throughflow code is used for the preliminary study of the curvature effect of the root flow path, and 3D RANS CFD calculations are then used to simulate the flow path from the inlet of the fan to the first stage of the core compressor. The adequacy of the application of the numerical code in this case has been assessed and confirmed by the comparison with the experimental data for two rig configurations. The results of this study show that the flow at the fan hub region is very complex and dominated by 3D effects. The interaction of the secondary flow with real geometries, such as leakage flows, is found to have a strong detrimental effect on the core performance. The curvature of the hub end wall is a key parameter controlling the fan root flow topology; it influences the strength of the secondary flow, the spanwise distribution of the flow, and its sensitivity to leakage flow. With this understanding, it is possible to redesign of the fan hub flow path to reduce the loss generation by a significant amount.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Side view of the fan stage module

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Figure 2

Core stator pressure distribution

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Figure 3

Turbofan core cycle

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Figure 4

Engine SFC: fan root loss effect

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Figure 5

Rotor grid: side view

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Figure 6

C-type splitter grid: side view

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Figure 7

Core stator grid: side view

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Figure 8

Extended grid of the core stator: side view

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Figure 9

Side view of rig A

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Figure 10

Side view of rig B

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Figure 11

Fan rear seal leakage path

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Figure 12

Rig A loss loop comparison

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Figure 13

Rig B loss loop comparison

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Figure 14

Rig A 0% leak. (i): TE flow distribution.

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Figure 15

Rig A 0% leak. (i): TE flow distribution.

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Figure 16

Rig A 1.5% leak. (j): TE flow distribution.

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Figure 17

Rig A 1.5% leak. (j): suction surface friction lines.

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Figure 18

Hub end wall definition

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Figure 19

Engine core stator loss loop

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Figure 20

Config. 1: suction surface friction lines

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Figure 21

Config. 2: suction surface friction lines

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Figure 22

Annulus contraction and hub curvature distribution

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Figure 23

Stator extraction planes

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Figure 24

Stator meridional velocity

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Figure 25

Config. 1 TE pressure distribution

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Figure 26

Config. 2 TE pressure distribution

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Figure 27

Core stator exit radial flow distribution

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Figure 28

Stator loss leakage sensitivity

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