On the Applicability of a Spoked-Wheel Wake Generator for Clocking Investigations

[+] Author and Article Information
Sven König

Turbomachinery Laboratory (TFA), Darmstadt University of Technology, 64287 Darmstadt, Germanykoenig@tfa.tu-darmstadt.de

Bernd Stoffel

Turbomachinery Laboratory (TFA), Darmstadt University of Technology, 64287 Darmstadt, Germany

J. Fluids Eng 129(11), 1468-1477 (May 14, 2007) (10 pages) doi:10.1115/1.2799523 History: Received September 28, 2006; Revised May 14, 2007

A comprehensive investigation was carried out using two different experimental setups: A 1.5-stage axial turbine and a simplified model, a “spoked-wheel” setup with a rotating wake generator consisting of cylindrical bars. The second stator of the turbine was designed at MTU Aero Engines as a high-lift profile with a Reynolds number typical for low-pressure turbines in jet engines. At design conditions, the flow on the stator 2 suction side features a pronounced separation bubble. To study the behavior of the stator 2 boundary layer and the interaction mechanisms between stator and rotor wakes, different measurement techniques were used: X-wire probes, five-hole probes, static pressure tappings, and surface mounted hot-film gauges. It was found that a rotating wake generator of the spoked-wheel type is not capable of resolving the relevant clocking mechanisms that occur in a real engine. However, such a simplified setup is useful to separate some of the physical mechanisms, and in case that the interaction of the stator 1 wakes with the stator 2 boundary layer is negligible, a spoked-wheel setup is well suited to simulate the influence of periodically incoming wakes on the transition behavior of stator 2.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

TU Darmstadt clocking facility

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Figure 2

Definition of the measuring planes

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Figure 3

Time-averaged static pressure distribution for different setups

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Figure 4

Normalized absolute velocity upstream of S2

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Figure 5

Flow angle upstream of S2

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Figure 6

Normalized stochastic fluctuations in x-direction upstream of S2

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Figure 7

Time-averaged RMSp-value (periodic) along S2 suction side

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Figure 8

Pitch-averaged integral flow angle downstream of S2

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Figure 9

Pitch-averaged integral turbulent kinetic energy downstream of S2

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Figure 10

Ensemble-averaged absolute velocity, turbulent kinetic energy, and flow angle upstream of S2 for y∕s=0.0 (blue/dashed line: clp=0.063, green/chain dotted line: clp=−0.125, red/solid line: clp=−0.375)

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Figure 11

ST diagrams of ensemble-averaged QWSS along stator 2 suction side, clp=0.063




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