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Research Papers: Gas Turbines: Turbomachinery

Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines—Part I: Numerical Validation of Wet Steam Models and Turbine Modeling

[+] Author and Article Information
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

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

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

F. Sieverding

Siemens AG,
Energy Sector,
Rheinstrasse 100,
Mülheim (Ruhr) D-45478, Germany
e-mail: frank.sieverding@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), 042602 (Oct 28, 2014) (11 pages) Paper No: GTP-14-1442; doi: 10.1115/1.4028468 History: Received July 28, 2014; Revised August 08, 2014

In this publication, an overview of the current state of wetness modeling at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) is given. For the modeling, an Euler–Euler method implemented in the commercial flow solver Ansys CFX is used. This method is able to take into account the nonequilibrium state of the steam and models the interactions between the gaseous and liquid phases. This paper is the first part of a two-part publication and deals with the numerical validation of wet steam models by means of condensing nozzle and cascade flows. A number of issues with regard to the quality of the computational fluid dynamics (CFD) code and the applied condensation models are addressed comparing the results to measurements. It can be concluded that a calibration of the models is necessary to achieve a satisfying agreement with the experimental results. Moreover, the modeling of the low pressure model steam turbine operated at the ITSM is described focusing on the asymmetric flow field in the last stage caused by the axial–radial diffuser. Different simplified axisymmetric diffuser models are investigated in steady state simulations, and the results and the arising issues for part-load, design-load, and over-load conditions are discussed. Thereafter, a comparison between the equilibrium and nonequilibrium steam modeling approaches is performed and the advantage of the nonequilibrium model is highlighted. The second part of the publication focuses on experimental investigations and compares the numerical results to wetness measurement data. For this purpose, different loads are also considered.

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References

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Schatz, M., and Eberle, T., 2014, “Experimental Study of Steam Wetness in a Model Steam Turbine Rig: Presentation of Results and Comparison With Computational Fluid Dynamics Data,” Proc. Inst. Mech. Eng., Part A, 228(2), pp. 129–142. [CrossRef]
Eberle, T., Schatz, M., Starzmann, J., Grübel, M., and Casey, M. V., 2014, “Experimental Study of the Effects of Temperature Variation on Droplet Size and Wetness Fraction in a Low Pressure Model Steam Turbine,” Proc. Inst. Mech. Eng., Part A, 228(1), pp. 97–106. [CrossRef]
Starzmann, J., Kaluza, P., Casey, M. V., and Sieverding, F., 2014, “On Kinematic Relaxation and Deposition of Water Droplets in the Last Stages of Low Pressure Steam Turbines,” ASME J. Turbomach., 136(7), p. 071001. [CrossRef]
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Schatz, M., Eberle, T., Grübel, M., Starzmann, J., Vogt, D. M., and Sürken, N., 2014, “Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines—Part II: Turbine Wetness Measurement and Comparison to CFD-Predictions,” ASME J. Gas Turbines Power, 137(4), p. 042603. [CrossRef]

Figures

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Fig. 1

Geometry of the Moses and Stein nozzle

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Fig. 2

Results for experiment no. 257

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Fig. 3

Results for experiment no. 203

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Fig. 4

Geometry of the White cascade and boundary conditions for the cases L1 and L2

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Fig. 5

Surface pressure profile for case L1

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Fig. 6

Representation of the trailing edge geometry

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Fig. 7

Surface pressure profile for case L2

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Fig. 8

Wetness at the traverse plane for case L1

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Fig. 9

Droplet diameter at the traverse plane for case L1

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Fig. 10

The model steam turbine test rig. From left to right: water brake, rotor of first two stages, rotor of last stage, and auxiliary turbine.

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Fig. 11

Numerical model of the model steam turbine including evaluation planes and definition of liquid phases

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Fig. 12

Supply pipes to the turbine inlet

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Fig. 13

CFD-diffuser models

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Fig. 14

Static pressure at plane E32 at design load

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Fig. 15

Measured and predicted total-static efficiency of the three stage turbine

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Fig. 16

Isosurfaces for a nucleation rate of J = 1018m−3 s−1 in the second stage at design load with and without calibration of the nucleation rate using the droplet growth model of Young [13]

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Fig. 17

Relative Mach number distribution at 70% span of the second rotor R2 at design load

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Fig. 18

Blade surface pressure of the second rotor R2 at design load

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Fig. 19

Wetness distributions at the evaluation planes E21 and E30 at design load

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