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Research Papers

Experimental Investigation of the Clocking Effect in a 1.5-Stage Axial Turbine—Part II: Unsteady Results and Boundary Layer Behavior

[+] Author and Article Information
Sven König

Turbomachinery Laboratory (TFA), Darmstadt University of Technology, 64287 Darmstadt, Germanykoenig.sven@siemens.com

Bernd Stoffel

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

M. Taher Schobeiri

Turbomachinery Performance Laboratory, Texas A&M University, College Station, TX 77843-3123

J. Turbomach 131(2), 021004 (Jan 22, 2009) (8 pages) doi:10.1115/1.2948969 History: Received September 28, 2006; Revised March 05, 2007; Published January 22, 2009

Comprehensive experimental investigations were conducted to get deeper insight into the physics of stator clocking in turbomachines. Different measurement techniques were used to investigate the influence of varying clocking positions on the highly unsteady flow field in a 1.5-stage axial low-pressure (LP) turbine. A Reynolds number typical for LP turbines as well as a two-dimensional blade design were chosen. Stator 2 was developed as a high-lift profile with a separation bubble on the suction side. This paper presents the results that were obtained by means of unsteady x-wire measurements upstream and downstream of Stator 2 and surface mounted hot-film measurements on the Stator 2 suction side. It was found that for the case when the Stator 1 wakes impinge close to the leading edge of Stator 2 the interaction between the Stator 1 and the rotor vortical structures takes place in proximity of the Stator 2 boundary layer, which leads to a shift of the transition point in the upstream direction. The major loss parameter concerning the Stator 2 aerodynamic performance could be attributed to the strength of the periodic fluctuations within the Stator 2 suction side boundary layer. A phase shift in the quasiwall shear stress signal in the front region of the Stator 2 vane was observed for different clocking positions.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 5

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

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Figure 6

Integral RMSp value (periodic) along the S2 suction side for different clp’s

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Figure 7

ST diagrams of ensemble-averaged flow quantities along the Stator 2 suction side

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Figure 8

Ensemble-averaged time traces along the S2 SS and upstream of S2 (blue/dashed line: clp=0.063, green/chain dotted line: clp=−0.125, red/solid line: clp=−0.375)

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Figure 1

Time-averaged QWSS along the S2 suction side

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Figure 2

Time-averaged QWSS along the S2 suction side (reattachment region)

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Figure 3

Time-averaged RMS value (stochastic) along the S2 suction side

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Figure 4

Time-averaged skewness along the S2 suction side

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