On the sloshing free surface in the draft tube cone of a Francis turbine operating in synchronous condenser mode

Vagnoni, Elena; Andolfatto, Loïc; Avellan, François

doi:10.1088/1742-6596/813/1/012034

Cited by 6 publications

(7 citation statements)

References 2 publications

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“…The effects of the relative rotation of a surrounding heavy fluid, such as water (the normal fluid in the operation of hydropower units), which have been discussed in previous papers [19,43,55], are not considered in this case and will be analyzed in a future paper. The validity of this analysis is therefore for large centrifugal compressors (which work in air and with relative low rotating speed) and hydropower units working in synchronous condenser mode [56,57], and serve as a basis for future considerations of the effect of a surrounding heavy fluid (water) in hydropower units. Figure 17.…”

Section: Validity Of the Relationship Between The Mode Shape Decomposmentioning

confidence: 96%

Experimental Measurements of the Natural Frequencies and Mode Shapes of Rotating Disk-Blades-Disk Assemblies from the Stationary Frame

et al. 2019

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Determining the natural frequencies and mode shapes of rotating turbomachinery components from both rotating and stationary reference frames is of paramount importance to avoid resonance problems that could affect the normal operation of the machine, or even cause critical damages in these components. Due to their similarity to real engineering cases, this topic has been experimentally analyzed in the past for disk-shaft assemblies and rotor disk-blades assemblies (bladed-disk or blisk). The same topic is less analyzed for disk-blades-disk assemblies, although such configurations are widely used in centrifugal closed impellers of compressors, hydraulic pumps, pump-turbines, and runners of high head Francis turbines. In this paper, experimental measurements, varying the rotating speed of a disk-blade-disk assembly and exciting the first natural frequencies of the rotating frame, have been performed. The rotating structure is excited and measured by means of PZT patches from the rotating frame and with a Laser Doppler Vibrometer (LDV). In order to interpret the experimental results obtained from the stationary frame, a method to decompose the diametrical mode shapes of the structure in simple diametrical components (which define the diametrical mode shapes of a simple disk) has been proposed. It is concluded that the resonant frequencies detected with a stationary sensor correspond to the ones predicted with the decomposition method. Finally, a means to obtain equivalent results with numerical simulation methods is shown.

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Section: Validity Of the Relationship Between The Mode Shape Decomposmentioning

confidence: 96%

Experimental Measurements of the Natural Frequencies and Mode Shapes of Rotating Disk-Blades-Disk Assemblies from the Stationary Frame

et al. 2019

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“…It is observed that the excitation from the RSI decreases a lot when entering to the SC mode but it is still existing, which means that there is still some interaction with the two-phase flow inside the runner and the guide vanes, as seen in Refs. [7,[9][10][11][12][13]. In these plots, the rotating speed of the runner (f f ) is also clearly seen at 2.14 Hz as well as its second harmonic (2f f ).…”

Section: Time-frequencymentioning

confidence: 98%

“…During SC operation, toque and power swings are experienced sometimes which an unclear origin [7,8]. Difficult flow conditions are occurring during this operation since the runner rotating in air induces a motion of the free surface, sometimes exciting sloshing modes of this [9,10]. Furthermore, the sloshing motion of this free surface induces also a mixture of air and water that can enter into the rotating runner, creating a difficult to predict two-phase flow behavior.…”

mentioning

confidence: 99%

“…Another problem that can happen during SC operation is that the water used for the labyrinth seals cooling goes into the vaneless gap between the closed guide vanes and the runner, causing an effect similar to the wellknown Rotor Stator Interaction (RSI). All these phenomena related with the flow behavior at this condition have been addressed in different studies based on reduced scale models [7,[9][10][11][12][13]. However, the effect of the SC operation into the runner stress or machine vibrations of Francis turbine prototypes has not been studied in the past.…”

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confidence: 99%

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Synchronous condenser operation in Francis turbines: Effects in the runner stress and machine vibration

et al. 2020

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“…If this process lasts for a longer time, a rotating wave develops on the water surface. This phenomenon is called oscillating water surface or sloshing and was investigated (2017) by [17]. This air-water system's excitation mechanism is still not proven from a fluid mechanics point of view.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Strength Analysis of a Prototype Francis Turbine in a Multilevel Lifetime Assessment Procedure Part II: Method Application and Numerical Investigation

et al. 2022

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Part I of the publication series addressed the fundamentals of lifetime assessment of prototype Francis turbines. This paper (Part II) focuses on the numerical part of the procedure. The essential steps and requirements shall be presented (background). The starting points for the numerical considerations are the pressure fields of the transient CFD simulations, which are exported per time step and applied to the existing structure via a fluid–structure interaction. That enables a transient mechanical stress calculation to be conducted, resulting in the fatigue analysis of the component to estimate the remaining lifetime. The individual model requirements should be represented accordingly and applied to the prototype facility (method). The results obtained from this application should be discussed and evaluated. It has to be mentioned that the validation of the numerical results will be performed at Part IV of this publication series (results). The present paper will end up discussing the results and conclusions about further data processing (Conclusion).

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On the sloshing free surface in the draft tube cone of a Francis turbine operating in synchronous condenser mode

Cited by 6 publications

References 2 publications

Experimental Measurements of the Natural Frequencies and Mode Shapes of Rotating Disk-Blades-Disk Assemblies from the Stationary Frame

Experimental Measurements of the Natural Frequencies and Mode Shapes of Rotating Disk-Blades-Disk Assemblies from the Stationary Frame

Synchronous condenser operation in Francis turbines: Effects in the runner stress and machine vibration

Fatigue Strength Analysis of a Prototype Francis Turbine in a Multilevel Lifetime Assessment Procedure Part II: Method Application and Numerical Investigation

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