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TECHNICAL PAPERS

Investigation on a Type of Flow Control to Weaken Unsteady Separated Flows by Unsteady Excitation in Axial Flow Compressors

[+] Author and Article Information
Xin-qian Zheng, Xiao-bo Zhou, Sheng Zhou

 Chinese National Key Laboratory of Aerodynamics and Thermodynamics of Aeroengine, Beijing University of Aeronautics and Astronautics, Beijing, 100083, P. R. China

J. Turbomach 127(3), 489-496 (Mar 01, 2004) (8 pages) doi:10.1115/1.1860572 History: Received October 01, 2003; Revised March 01, 2004

By solving unsteady Reynolds-averaged Navier-Stokes equations discretized by a high-order scheme, the results showed that the disordered unsteady separated flow could be effectively controlled by periodic suction and blowing in a wide range of incidences, resulting in enhancement of time-averaged aerodynamic performances of an axial compressor cascade. The effects of unsteady excitation frequency, amplitude, and excitation location were investigated in detail. The effective excitation frequency spans a wide spectrum, and there is an optimal excitation frequency that is nearly equal to the characteristic frequency of vortex shedding. Excitation amplitude exhibits a threshold value (nearly 10% in terms of the ratio of maximum velocity of periodic suction and blowing to the velocity of free flow) and an optimal value (nearly 35%). The optimal excitation location is just upstream of the separation point. We also explored feasible unsteady actuators by utilizing the upstream wake for constraining unsteady separation in axial flow compressors.

Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Computational domain and instantaneous vorticity field without excitation at i=10deg

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Figure 2

Time domain graph of total pressure at i=10deg

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Figure 3

Spectrum of total pressure at i=10deg

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Figure 4

Loss coefficient at different incidences, excited versus unexcited

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Figure 5

Ratio of static pressure at different incidences, excited versus unexcited

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Figure 6

Instantaneous vorticity field by computation at i=10deg, unexcited

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Figure 7

Instantaneous vorticity field by computation at i=10deg, excited

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Figure 8

Time-averaged vorticity field by computation at i=10deg, unexcited

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Figure 9

Time-averaged vorticity field by computation at i=10deg, excited

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Figure 10

Phase diagram at some fixed point on the exit section of cascade at i=10deg: (a) unexcited and (b) excited

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Figure 11

Instantaneous Vorticity Field by PIV, unexcited

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Figure 12

Instantaneous Vorticity Field by PIV, excited

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Figure 13

Loss coefficient for different relative excitation frequency (A¯=30% and i=10deg)

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Figure 14

Loss coefficient for different relative excitation amplitude (f¯e=1 and i=10deg)

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Figure 15

Loss coefficient for different excitation location (f¯e=1, A¯=30%, i=10deg)

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