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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

Numerical Investigation on the Time-Variant Flow Field and Dynamic Forces Acting in Steam Turbine Inlet Valves

[+] Author and Article Information
Clemens Bernhard Domnick

University of Duisburg-Essen,
Forsthaus Weg 1,
Duisburg 47057, Germany
e-mail: bernhard.domnick@uni-due.de

Friedrich-Karl Benra, Hans Josef Dohmen

University of Duisburg-Essen,
Forsthaus Weg 1,
Duisburg 47057, Germany

Dieter Brillert

University of Duisburg-Essen,
Forsthaus Weg 1
Duisburg 47057, Germany

Christian Musch

Steam Turbines,
Siemens AG,
Rheinstraße 100,
Mülheim an der Ruhr 45478, Germany

Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 31, 2014; final manuscript received August 15, 2014; published online January 28, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(8), 081601 (Aug 01, 2015) (11 pages) Paper No: GTP-14-1452; doi: 10.1115/1.4029309 History: Received July 31, 2014; Revised August 15, 2014; Online January 28, 2015

The unsteady flow in inlet valves for large steam turbines used in power stations was investigated using the method of computational fluid dynamics (CFD). As the topology of the flow depends on the stroke and the pressure ratio of the valve, the flow was investigated at several positions. Various turbulence models were applied to the valve to capture the unsteady flow field. Basic Reynolds-averaged Navier–Stokes (RANS) models, the scale adaptive simulation (SAS), and the scale adaptive simulation with zonal forcing (SAS-F, also called ZFLES) were evaluated. To clarify the cause of flow-induced valve vibrations, the investigation focused on the pressure field acting on the valve plug. It can be shown that acoustic modes are excited by the flow field. These modes cause unsteady forces that act on the valve plug. The influence of valve geometry on the acoustic eigenmodes was investigated to determine how to reduce the dynamic forces. Three major flow topologies that create different dynamic forces were identified.

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References

Figures

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Fig. 5

Grid resolution at the seat and the diffuser

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Fig. 4

Normalized pressure distribution at the diffuser wall

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Fig. 3

Resolution of the boundary layer

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Fig. 2

Valve characteristic and simulated OPs

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Fig. 1

Model of the valve

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Fig. 6

Sketch of Nakano et al. [5] test rig

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Fig. 7

Force spectra obtained with various turbulence models

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Fig. 14

Normalized axial force spectrum at OP 1

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Fig. 15

Comparison between modal shape and normalized pressure fluctuations at OP 1

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Fig. 12

Time-averaged Mach number distribution and distribution of normalized pressure fluctuations at OP 1

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Fig. 13

Time-averaged Mach number distribution upstream of the valve cone

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Fig. 8

Influence of the time step on the calculated force spectra

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Fig. 9

Sketch of the test rig built by Krothapalli et al. [21]

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Fig. 10

Sound pressure levels calculated with the SAS-F and SAS turbulence models

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Fig. 11

Instantaneous Mach number distribution in the valve diffuser calculated with various turbulence models at OP 3

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Fig. 16

Force spectrum of the transverse force acting on the valve plug at OP 1

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Fig. 17

Time-averaged Mach number field and normalized pressure fluctuations at OP 3

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Fig. 18

Force spectra of the axial force acting on the valve plug

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Fig. 19

Calculated Strouhal number of the acoustic mode versus the valve stroke

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Fig. 20

Vortices in the shear layer

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Fig. 25

Distribution of the St = 0.59 peak in the valve seat at OP 3

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Fig. 21

Normalized axial force spectra

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Fig. 22

Force spectrum of the transverse force acting on the valve plug at OP 2

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Fig. 23

Force spectra of the transverse force acting on the valve plug

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Fig. 24

Spectrum of normalized pressure fluctuations in the valve diffuser

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Fig. 26

Force spectrum of the transverse force acting on the valve plug at OP 4

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Fig. 27

Flow separation at the valve diffuser

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Fig. 28

Time-averaged Mach number field and normalized pressure fluctuations at OP 6

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Fig. 29

Axial force spectra

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Fig. 30

Transverse force spectrum

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Fig. 31

Time-averaged Mach number field and normalized pressure fluctuations at OP 5

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Fig. 32

Distribution of the normalized time-averaged pressure in the valve diffuser at OP 5

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Fig. 33

Classification of the flow topology

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Fig. 34

Comparison of axial force spectra for standard and enlarged bores at OP 1

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