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Research Papers: Flows in Complex Systems

Long-Period Pressure Pulsation Estimated in Numerical Simulations for Excessive Flow Rate Condition of Francis Turbine

[+] Author and Article Information
Kenji Shingai

Hitachi Research Laboratory, Hitachi, Ltd.
832-2 Horiguchi, Hitachinaka-shi,
Ibaraki 312-0034, Japan
e-mail: kenji.shingai.vd@hitachi.com

Nobuaki Okamoto

Shikoku Electric Power Co., Inc.,
2-5 Marunouchi, Takamatsu-shi,
Kagawa 760-8573, Japan

Yuta Tamura

Basic Engineering/Hydraulic Laboratory,
Hitachi Mitsubishi Hydro Co.,
3-2-1 Saiwai, Hitachi-shi,
Ibaraki 317-0073, Japan

Kiyohito Tani

Basic Engineering/Hydraulic Laboratory,
Hitachi Mitsubishi Hydro Co.,
3-2-1 Saiwai, Hitachi-shi,
Ibaraki 317-0073, Japan
e-mail: tani.kiyohito.rg@hm-hydro.com

1Present affiliation is Mitsubishi Hitachi Power Systems, Ltd., Yokohama, Japan, e-mail: kenji_shingai@mhps.com

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received August 28, 2013; final manuscript received January 17, 2014; published online May 7, 2014. Assoc. Editor: Frank C. Visser.

J. Fluids Eng 136(7), 071105 (May 07, 2014) (9 pages) Paper No: FE-13-1521; doi: 10.1115/1.4026584 History: Received August 28, 2013; Revised January 17, 2014

A series of numerical simulations for a Francis turbine were carried out to estimate the unsteady motion of the cavity in the draft tube of the turbine under a much larger flow rate condition than the swirl-free flow rate. The evaporation and condensation process was described by using a simplified Rayleigh–Plesset equation. A two-phase homogeneous model was adopted to calculate the mixture of gas and liquid phases. Instantaneous pressure monitored at a point on the draft tube formed long-period pulsations. Detailed analysis of the simulation results clarified the occurrence of a uniquely shaped cavity and the corresponding flow pattern in every period of the pressure pulsations. The existence of a uniquely shaped cavity was verified with an experimental approach. A simulation without rotor-stator interaction also obtained long-period pulsations after an extremely long computational time. This result shows that the rotor-stator interaction does not contribute to the excitation of long-period pulsations.

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References

Figures

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Fig. 1

Meridional section of flow passage in the runner

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Fig. 2

Grid for rotor-stator interaction simulation

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Fig. 3

Grids for one component simulation

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Fig. 7

Shapes of cavity, section velocity, and section static pressure profiles for smaller flow rate Q/Qsf = 0.6217

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Fig. 6

Pressure pulsation estimated by RSI simulation in excessive flow rates Q/Qsf = 1.208

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Fig. 5

Pressure pulsation estimated by RSI simulation in smaller flow rate Q/Qsf = 0.6217

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Fig. 4

Comparison of turbine efficiencies obtained in RSI simulations and model test

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Fig. 8

Shapes of cavity, section velocity, and section static pressure profiles for excessive flow rate Q/Qsf=1.208

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Fig. 9

Mass-weighted averaged velocity profiles at z* = -0.4894,-0.9351, and-1.418 in tn = 44.97 for the excessive flow rate Q/Qsf = 1.208

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Fig. 10

Mass-weighted averaged velocity profiles at z* = -0.4894,-0.9351, and-1.418 in tn = 49.97 for the excessive flow rate Q/Qsf = 1.208

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Fig. 11

History of swirl intensity and lowest edge position of cavitation

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Fig. 12

Pressure pulsation estimated by 1-C simulation in smaller flow rate Q/Qsf = 0.6217

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Fig. 13

Pressure pulsation estimated by 1-C simulation in excessive flow rates Q/Qsf = 1.208

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