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Research Papers: Gas Turbines: Turbomachinery

Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines—Part II: Turbine Wetness Measurement and Comparison to Computational Fluid Dynamics-Predictions

[+] Author and Article Information
M. Schatz

ITSM—Institute of Thermal Turbomachinery and
Machinery Laboratory,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany
e-mail: schatz@itsm.uni-stuttgart.de

T. Eberle

ITSM—Institute of Thermal Turbomachinery and
Machinery Laboratory,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany
e-mail: eberle@itsm.uni-stuttgart.de

M. Grübel

ITSM—Institute of Thermal Turbomachinery and
Machinery Laboratory,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany
e-mail: gruebel@itsm.uni-stuttgart.de

J. Starzmann

ITSM—Institute of Thermal Turbomachinery and
Machinery Laboratory,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany
e-mail: starzmann@itsm.uni-stuttgart.de

D. M. Vogt

ITSM—Institute of Thermal Turbomachinery and
Machinery Laboratory,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany
e-mail: vogt@itsm.uni-stuttgart.de

N. Suerken

Siemens AG, Energy Sector,
Rheinstrasse 100,
Mülheim (Ruhr) D-45478, Germany
e-mail: norbert.suerken@siemens.com

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 28, 2014; final manuscript received August 8, 2014; published online October 28, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(4), 042603 (Oct 28, 2014) (9 pages) Paper No: GTP-14-1443; doi: 10.1115/1.4028547 History: Received July 28, 2014; Revised August 08, 2014

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosion. Despite the fact that there are many computational fluid dynamics (CFD)-packages that can deal with real-gas effects in steam flows, the accurate and reliable prediction of subcooling, condensation, and wet steam flow in steam turbines using CFD is still a demanding task. One reason for this is the lack of validation data for turbines that can be used to assess the physical models applied. Experimental data from nozzle and cascade tests can be found in the open literature; however, these measurement results are only partly useful for validation purposes for a number of reasons. With regard to steam turbine test data, there are some publications, yet always without any information about the turbine stage geometries. This publication is part of a two-part paper; whereas Part I focuses on the numerical validation of wet steam models by means of condensing nozzle and cascade flows, the focus in this part lies on the comparison of CFD results of the turbine flow to experimental data at various load conditions. In order to assess the validity and reliability of the experimental data, the method of measurement is presented in detail and discussed. The comparison of experimental and numerical results is used for a discussion about the challenges in both modeling and measuring steam turbine flows, presenting the current experience and knowledge at Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM).

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References

Figures

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Fig. 1

Extinction coefficient as function of the Mie-parameter for mr = 1.33

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Fig. 2

Examples of extinction curves for different polydisperse droplet populations

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Fig. 3

Examples of extinction curves for monomodal and bimodal droplet populations

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Fig. 4

Sectional view of the turbine with measuring plane E30

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Fig. 5

Front view and cross section of the combined wetness/pressure probe used

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Fig. 6

Static pressure, total pressure, and Mach number along the channel height at part load condition

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Fig. 7

Static pressure, total pressure, and Mach number along the channel height at design load

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Fig. 8

Static pressure, total pressure, and Mach number along the channel height at overload condition

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Fig. 9

Steam wetness, measured D32, and predicted droplet diameters of p1 and p2 at part load condition

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Fig. 10

Steam wetness, measured D32, and predicted droplet diameters of p1 and p2 at design load

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Fig. 11

Steam wetness, measured D32, and predicted droplet diameters of p1 and p2 at overload condition

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Fig. 12

Comparison of measured and predicted total-static efficiency of the model steam turbine, from Ref. [1]

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