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TECHNICAL PAPERS

Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry

[+] Author and Article Information
E. Göttlich

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz, Styria A-8010, Austriaemil.goettlich@tugraz.at

J. Woisetschläger, P. Pieringer, B. Hampel, F. Heitmeir

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz, Styria A-8010, Austria

J. Turbomach 128(1), 178-187 (Feb 01, 2005) (10 pages) doi:10.1115/1.2103092 History: Received October 01, 2004; Revised February 01, 2005

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Meridional flow path and measurement planes

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Figure 2

Profiles at trigger zero position

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Figure 3

LDV measurement locations

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Figure 4

Velocity decomposition for phase averaged data

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Figure 5

General arrangement of PIV system

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Figure 6

PIV measurement locations

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Figure 7

Time-space plots of turbulent kinetic energy in plane B1 and C1 at midspan measured by LDV

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Figure 8

Time-space plots of velocity and yaw angle in plane B1 at different radii measured by LDV

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Figure 9

Time-space plots of velocity and turbulent kinetic energy in plane C1 at different radii measured by LDV

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Figure 10

Nozzle wake at 50% span, lines indicate isobars, grayscale indicate entropy

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Figure 11

Time-resolved stereoscopic PIV results showing velocity distributions at midspan

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Figure 12

Time-resolved stereoscopic PIV results showing yaw angle distributions at midspan

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Figure 13

Time-resolved stereoscopic PIV results showing vorticity distributions at midspan

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Figure 14

Unsteady CFD results showing vorticity distributions at midspan

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