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TECHNICAL PAPERS

Numerical Study of Active Flow Control for a Transitional Highly Loaded Low-Pressure Turbine

[+] Author and Article Information
Donald P. Rizzetta

 Air Force Research Laboratory, Computational Sciences Branch, Aeronautical Sciences Division, AFRL/VAAC, Building 146 - Room 225, 2210 Eighth Street, Wright-Patterson AFB, OH 45433-7512donald.rizzetta@afrl.af.mil

Miguel R. Visbal

 Air Force Research Laboratory, Computational Sciences Branch, Aeronautical Sciences Division, AFRL/VAAC, Building 146 - Room 225, 2210 Eighth Street, Wright-Patterson AFB, OH 45433-7512miguel.visbal@afrl.af.mil

J. Fluids Eng 128(5), 956-967 (Mar 09, 2006) (12 pages) doi:10.1115/1.2238877 History: Received November 29, 2005; Revised March 09, 2006

Active control was simulated numerically for the subsonic flow through a highly loaded low-pressure turbine. The configuration approximated cascade experiments that were conducted to investigate a reduction in turbine stage blade count, which can decrease both weight and mechanical complexity. At a nominal Reynolds number of 25,000 based upon axial chord and inlet conditions, massive separation occurred on the suction surface of each blade due to uncovered turning. Vortex generating jets were then used to help mitigate separation, thereby reducing wake losses. Computations were performed using both steady blowing and pulsed mass injection to study the effects of active flow control on the transitional flow occurring in the aft-blade and near-wake regions. The numerical method utilized a centered compact finite-difference scheme to represent spatial derivatives, that was used in conjunction with a low-pass Pade-type nondispersive filter operator to maintain stability. An implicit approximately factored time-marching algorithm was employed, and Newton-like subiterations were applied to achieve second-order temporal accuracy. Calculations were carried out on a massively parallel computing platform, using domain decomposition to distribute subzones on individual processors. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are described, and simulations are compared with each other, with available experimental data, and with a previously obtained baseline case for the noncontrolled flow. It was found that active flow control was able to maintain attached flow over an additional distance of 19–21% of the blade chord, relative to the baseline case, which resulted in a reduction of the wake total pressure loss coefficient of 53–56%.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic representation of the turbine blade configuration and vortex generator jet geometry

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Figure 2

Turbine blade computational mesh system

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Figure 3

Jet blowing ratio time history

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Figure 4

Time-mean surface pressure coefficient distributions

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Figure 5

Time-mean velocity magnitude profiles at upstream stations

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Figure 6

Time-mean velocity magnitude profiles at downstream stations

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Figure 7

Time-mean turbulent kinetic energy spanwise wave-number spectra

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Figure 16

Instantaneous planar contours of the streamwise component of vorticity for the steady injection case, and the pulsed injection case at t∕tp=0.5 and t∕tp=1.0

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Figure 15

Instantaneous iso-surfaces of vorticity magnitude in the near-jet region

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Figure 14

Instantaneous planar contours of the spanwise component of vorticity on the blade surface

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Figure 13

Instantaneous iso-surfaces of vorticity magnitude in the trailing-edge region

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Figure 12

Instantaneous planar contours of the spanwise component of vorticity

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Figure 11

Turbulent kinetic energy frequency spectra

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Figure 10

Time-mean fluctuating velocity magnitude profiles

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Figure 9

Time-mean contours of the spanwise component of vorticity on the blade surface

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Figure 8

Time-mean contours of the spanwise component of vorticity

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