Mechanical impact of dynamic phenomena in Francis turbines at off design conditions

Duparchy, F.; Brammer, James; Thibaud, M.; Favrel, Arthur; Lowys, P. Y.; Avellan, François

doi:10.1088/1742-6596/813/1/012035

Cited by 13 publications

(12 citation statements)

References 2 publications

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“…17 shows the experimental and simulation results of dynamic strain at part-load conditions under the influence of the precessing vortex rope. In this case, the low frequency components of the signal were accurately predicted, while the high components (such as RSI) could not be captured as the time step was not small enough [101].…”

Section: Part Loadmentioning

confidence: 99%

“…The dynamic stresses in a part load condition (with the presence of the vortex rope) have been predicted with numerical simulation models recently [68,101]. The estimation of the pressure loads with the CFD model is more complex in this case, since cavitation phenomenon needs to be considered.…”

Section: Part Loadmentioning

confidence: 99%

“…The estimation of the pressure loads with the CFD model is more complex in this case, since cavitation phenomenon needs to be considered. In such case, the election of the cavitation model has to be evaluated and a sensitivity analysis for the different models may be performed [101]. As the vortex rope is a low frequency phenomenon, more simulated time needs to be considered which implies longer computational time.…”

Section: Part Loadmentioning

confidence: 99%

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Fatigue life estimation of Francis turbines based on experimental strain measurements: Review of the actual data and future trends

Presas

Luo

Wang

et al. 2019

Renewable and Sustainable Energy Reviews

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Due to the massive entrance of new renewable energies such as wind or solar, hydraulic turbines have to work far from its designed point and withstanding multiple transients, such as starts and stops, that shorten the useful life of the machine and cause fatigue damages. The present paper reviews the complex problem of fatigue in Francis turbines particularly focused on the experimental data available for static and dynamic stresses. For this purpose, many researches, which include different Francis turbines covering a wide range of design head and power, have been considered. The experimental stresses characteristics measured with strain gauges installed on the turbine runner and obtained from previous works have been analyzed for the different operating conditions and transient states occurring in the normal life of actual Francis units. The actual computational capabilities and techniques typically used to estimate such stresses have been discussed in detail. Potential future techniques to simplify complex strain measurements on the turbine runner, computational and statistical methods to estimate turbine stresses are reviewed in this paper. Finally, the relative damage of the different operating conditions and useful life estimation of the turbine, based on past strain measurements of the runner, are addressed.

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Section: Part Loadmentioning

confidence: 99%

Section: Part Loadmentioning

confidence: 99%

Section: Part Loadmentioning

confidence: 99%

See 1 more Smart Citation

Fatigue life estimation of Francis turbines based on experimental strain measurements: Review of the actual data and future trends

Presas

Luo

Wang

et al. 2019

Renewable and Sustainable Energy Reviews

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“…At part load [37][38][39] (and sometimes at full load [40]), a vortex rope can appear. This vortex rope has a frequency below the rotational frequency of the runner and has the ability to excite the whole hydraulic system [37,[40][41][42].…”

Section: Vortex Ropementioning

confidence: 99%

Cavitation Effects on the Structural Resonance of Hydraulic Turbines: Failure Analysis in a Real Francis Turbine Runner

et al. 2018

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When discussing potential resonances in hydraulic turbine runners, cavitation effects are usually neglected. Nevertheless, recent studies have experimentally proved, that large cavitation volumes in the proximity of flexible simple structures, such as hydrofoils, greatly modify their natural frequencies.In this paper, we analyze a resonance case in a Francis runner that leads to multiple fractures on the trailing edge of the blades, after just one day of operation at deep part load. If simple acoustic Fluid-Structure-Interaction (FSI) simulations are used, where the runner's surrounding fluid is considered as a homogenous acoustic medium (water), the risk of structural resonances seems to be limited as the predicted natural frequencies are far enough from the excited frequencies by the flow. It is shown that the only hydraulic phenomenon which could have produced such fractures in the present case is the Rotor Stator Interaction (RSI). In order to analyze possible cavitation effects on the natural frequencies of the turbine runner, CFD simulations of the deep part load conditions have been performed, which predict large inter-blade vortex cavities. These cavities have been then introduced in the acoustical FSI model showing that under such conditions, natural frequencies of the runner increase approaching to some of the RSI excited frequencies. In particular, a possible resonance of the four-nodal diameter (4ND) mode has been found which would explain the fast behavior of the crack propagation. Furthermore, the shape and the position of the real fracture found agree with the local maximum stress spots at the junction between the trailing edges and the crown.Energies 2018, 11, 2320 2 of 16 almost one century ago. More recently, the researches of Amabili et al. [4,5] and Kwak [6] revise and improve the analytical work performed by Lamb. Furthermore, many studies performed in the last decade show that acoustical FSI simulations are perfectly capable to predict natural frequencies of submerged structures [7][8][9]. In all the aforementioned studies simple thin plates have been considered.In the particular case of reaction hydraulic Turbines, which are completely submerged, added mass effects play an important role and have to be considered for the calculation of the natural frequencies as well. In this case the added mass phenomenon is even more complicated, as the gaps turbine-casing (usually considered as rigid boundaries) are extremely small (less than 1% of the turbine diameter), the turbine is rotating, and the water couples the turbine with the casing. Some effects such as rotation [10], influence of non-rigid surfaces [11] and acoustic modes [12] have been recently discussed using numerical FSI simulations and contrasting experimental results. Nevertheless, most of these effects have not been yet determined in real turbines. A review of actual research works shows that for turbine runners in still water, natural frequencies and mode shapes obtained with finite element simulations have a good agreement with exp...

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“…It should be noted that the systems for monitoring and diagnostics of HPP's equipment are constantly evolving, taking into account the tightening requirements for the conditions of the unit's usage [3][4][5][6] and the changing regulatory framework [7][8][9]. In recent years, predictive self-learning systems using artificial intelligence and based on BIG DATA and MACHINE LEARNING (ML) technologies [10][11][12] have been actively introduced at various energy facilities.…”

Section: Introductionmentioning

confidence: 99%

Limitations of Modern Diagnostic and Prognostic Systems for a Hydraulic Unit’s Health

Georgievskaia

2021

Eng

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Modern diagnostic systems for the hydraulic unit’s health play an important role in ensuring the reliability and safety of the hydroelectric power plant (HPP). However, they cannot provide timely detection of such dangerous operational defects as fatigue cracks. This article reflects two main reasons for this problem. The first one is a high level of the individuality of hydraulic units, which does not allow the effective use of statistical methods of information processing, including BIG DATA and MACHINE LEARNING technologies. The second is the fundamental impossibility to identify cracks in some key components of hydraulic units only on the basis of data analysis from a standard diagnostic system usually used at the HPP. Developed computational studies on the example of Francis turbines confirmed this. It is proposed to supplement the functionality of standard diagnostic systems with a prognostic block for an individual analytical forecast of the unit’s residual lifetime based on the calculated assessment of fatigue strength. This article presents the developed conceptual diagram and the demonstration version of the proposed analytical predictive system. The comparison of the standard vibration diagnostic system and the proposed solution as a tool for the early detection of cracks in a Francis turbine runner shows some advantages of the proposed approach.

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Mechanical impact of dynamic phenomena in Francis turbines at off design conditions

Cited by 13 publications

References 2 publications

Fatigue life estimation of Francis turbines based on experimental strain measurements: Review of the actual data and future trends

Fatigue life estimation of Francis turbines based on experimental strain measurements: Review of the actual data and future trends

Cavitation Effects on the Structural Resonance of Hydraulic Turbines: Failure Analysis in a Real Francis Turbine Runner

Limitations of Modern Diagnostic and Prognostic Systems for a Hydraulic Unit’s Health

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