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Flows in Complex Systems

Study of Near-Stall Flow Behavior in a Modern Transonic Fan With Compound Sweep

[+] Author and Article Information
Chunill Hah

NASA Glenn Research Center MS 5–11, 21000 Brookpark Road,Cleveland, OH 44135Chunill.Hah-1@nasa.gov

Hyoun-Woo Shin

Aero Technology Lab, GE Aviation, 1 Neumann Way,Cincinnati, OH 45215hyoun-woo.shin@ge.com

J. Fluids Eng 134(7), 071101 (Jun 21, 2012) (7 pages) doi:10.1115/1.4006878 History: Received October 20, 2011; Revised May 18, 2012; Published June 21, 2012; Online June 21, 2012

Detailed flow behavior in a modern transonic fan with a compound sweep is investigated in this paper. Both unsteady Reynolds-averaged Navier-Stokes (URANS) and large eddy simulation (LES) methods are applied to investigate the flow field over a wide operating range. The calculated flow fields are compared with the data from an array of high-frequency response pressure transducers embedded in the fan casing. The current study shows that a relatively fine computational grid is required to resolve the flow field adequately and to calculate the pressure rise across the fan correctly. The calculated flow field shows detailed flow structure near the fan rotor tip region. Due to the introduction of compound sweep toward the rotor tip, the flow structure at the rotor tip is much more stable compared to that of the conventional blade design. The passage shock stays very close to the leading edge at the rotor tip even at the throttle limit. On the other hand, the passage shock becomes stronger and detaches earlier from the blade passage at the radius where the blade sweep is in the opposite direction. The interaction between the tip clearance vortex and the passage shock becomes intense as the fan operates toward the stall limit, and tip clearance vortex breakdown occurs at near-stall operation. URANS calculates the time-averaged flow field fairly well. Details of measured rms static pressure are not calculated with sufficient accuracy with URANS. On the other hand, LES calculates details of the measured unsteady flow features in the current transonic fan with compound sweep fairly well and reveals the flow mechanism behind the measured unsteady flow field.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Cross section of test fan

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Figure 2

View of casing with pressure block

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Figure 3

Three operating points for comparison

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Figure 4

Measured static pressure and rms static pressure at choke condition (point 1 in Fig. 3)

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Figure 5

Calculated static pressure and rms static pressure at choke condition (point 1 in Fig. 3), URANS

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Figure 6

Comparison of steady static pressure rise at choke condition (point 1 in Fig. 3)

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Figure 7

Measured static pressure and rms static pressure at peak efficiency condition (point 2 in Fig. 3)

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Figure 8

Calculated static pressure and rms static pressure at peak efficiency condition (point 2 in Fig. 3), URANS

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Figure 9

Calculated static pressure at 50% span at peak efficiency point

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Figure 10

Comparison of steady static pressure rise at peak efficiency condition (point 2 in Fig. 3)

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Figure 11

Measured static pressure and rms static pressure at near-stall condition (point 3 in Fig. 3)

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Figure 12

Calculated static pressure and rms static pressure at near stall condition (point 3 in Fig. 3), URANS

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Figure 13

Changes in static pressure distribution at the fan tip at near stall operation (point 3 in Fig. 3), LES

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Figure 14

Calculated static pressure and rms static pressure at near stall condition (point 3 in Fig. 3), LES

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Figure 15

rms static pressure distribution and averaged velocity vectors at fan tip, near stall (point 3 in Fig. 3), LES

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Figure 16

Comparison of steady static pressure rise at near stall condition (point 3 in Fig. 3)

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