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Research Papers

Experimental Investigation of the Clocking Effect in a 1.5-Stage Axial Turbine—Part I: Time-Averaged Results

[+] 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), 021003 (Jan 22, 2009) (12 pages) doi:10.1115/1.2948968 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 static pressure tappings and five-hole probes as well as the time-averaged results of unsteady x-wire measurements. The probes were traversed in different measuring planes for ten clocking positions. Depending on the clocking position, a variation in total pressure loss for Stator 2, a change of the rotor exit flow angle, and a dependency of the Stator 2 exit flow angle were found. The influence of these parameters on turbine efficiency was studied. Three main factors affecting the total pressure loss could be separated: the size of the separation bubble, the production of turbulent kinetic energy, and the strength of the periodic fluctuations downstream of Stator 2.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

TU Darmstadt clocking facility

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Figure 2

Definition of the clp

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Figure 3

Illustration of the ensemble-averaging technique

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Figure 4

Flow angle upstream of S2

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Figure 5

Pitch-averaged integral flow angle upstream of S2

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Figure 6

Normalized absolute velocity upstream of S2; S1 wake impinges on the S2 PS

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Figure 7

Normalized absolute velocity upstream of S2; S1 wake impinges on the S2 SS

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Figure 8

Normalized stochastic fluctuations in x-direction upstream of S2

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Figure 9

Normalized stochastic fluctuations in y-direction upstream of S2

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Figure 10

Turbulent kinetic energy upstream of S2

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Figure 11

Pitch-averaged integral turbulent kinetic energy upstream of S2

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Figure 12

Normalized periodic fluctuations of the absolute flow velocity upstream of S2

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Figure 13

Turbulent kinetic energy downstream of S2

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Figure 14

Pitch-averaged integral turbulent kinetic energy downstream of S2

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Figure 15

Normalized periodic fluctuations of the absolute flow velocity downstream of S2

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Figure 16

Pitch-averaged integral normalized periodic fluctuations of the absolute flow velocity downstream of S2

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Figure 17

Total pressure loss coefficient of S2; S1 wake impinges on the S2 PS

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Figure 18

Total pressure loss coefficient of S2; S1 wake impinges on the S2 SS

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Figure 19

Pitch-averaged integral total pressure loss coefficient of S2

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Figure 20

Pitch-averaged integral dynamic pressure coefficient of S2

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Figure 21

Pitch-averaged integral static pressure coefficient of S2

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Figure 22

Time-averaged static pressure distribution for different clp’s

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Figure 23

Flow angle downstream of S2; S1 wake impinges on the S2 PS

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Figure 24

Flow angle downstream of S2; S1 wake impinges on the S2 SS

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Figure 25

Pitch-averaged integral flow angle downstream of S2

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