Interaction between trailing edge wake and vortex rings in a Francis turbine at runaway condition: Compressible large eddy simulation

Trivedi, Chirag; Dahlhaug, Ole Gunnar

doi:10.1063/1.5030867

Cited by 43 publications

(18 citation statements)

References 53 publications

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“…The other high frequency of 24.0 times that of the runner rotational frequency belongs to the guide vane passing frequency. This particular RSI frequency (f gv ) was also detected by Trivedi et al [28,32].…”

Section: In Runnersupporting

confidence: 74%

Investigation of Pressure Fluctuation and Pulsating Hydraulic Axial Thrust in Francis Turbines

et al. 2020

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Under the circumstances of rapid expansion of diverse forms of volatile and intermittent renewable energy sources, hydropower stations have become increasingly indispensable for improving the quality of energy conversion processes. As a consequence, Francis turbines, one of the most popular options, need to operate under off-design conditions, particularly for partial load operation. In this paper, a prototype Francis turbine was used to investigate the pressure fluctuations and hydraulic axial thrust pulsation under four partial load conditions. The analyses of pressure fluctuations in the vaneless space, runner, and draft tube are discussed in detail. The observed precession frequency of the vortex rope is 0.24 times that of the runner rotational frequency, which is able to travel upstream (from the draft tube to the vaneless space). Frequencies of both 24.0 and 15.0 times that of the runner rotational frequency are detected in the recording points of the runner surface, while the main dominant frequency recorded in the vaneless zone is 15.0 times that of the runner rotational frequency. Apart from unsteady pressure fluctuations, the pulsating property of hydraulic axial thrust is discussed in depth. In conclusion, the pulsation of hydraulic axial thrust is derived from the pressure fluctuations of the runner surface and is more complicated than the pressure fluctuations.

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Section: In Runnersupporting

confidence: 74%

Investigation of Pressure Fluctuation and Pulsating Hydraulic Axial Thrust in Francis Turbines

et al. 2020

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“…Fortin et al [6,7] measured the pressure on the impeller blade surface during the runaway process to relate the pressure and the vortex rope. Trivedi et al [8,9] compared the pressure pulsation frequency with different blade angles during the runaway process. The high amplitude of the pressure pulsation may decrease the service life of the impeller blade.…”

Section: Introductionmentioning

confidence: 99%

Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

Liu

Huang²,

et al. 2021

Processes

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The runaway condition is a damage condition for pumps and turbines which can induce the wake vortex, reverse flow, and severe pressure pulsation. This study aimed to research the characteristics of pressure pulsation of axial flow pumps under different runaway conditions, and the runaway model test was performed with different blade angles and heads. Moreover, four pressure sensors were uniformly arranged at the impeller inlet section to eliminate the random error. The time domain and frequency domain analysis were the main methods to obtain the change regulations. Results showed that the pressure pulsation under the runaway condition are mainly influenced by the rotation frequency, blade passing frequency, and wake vortex frequency. The dimensionless pressure pulsation coefficient of rotation frequency and wake vortex frequency increased obviously with the runaway head increasing, but changed little with different blade angles. In addition, the dimensionless pressure coefficient of wake vortex frequency of the sensors around the impeller inlet section differed a lot, which means that the wake vortex core is not in center of the rotation axis. The average dimensionless pressure pulsation coefficient of wake vortex frequency is higher than that of rotation frequency with the same runaway head, owing to the severer wake vortex.

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“…This condition is also one of the most damaging condition due to its high amplitude stresses [32,68,87,92,93]. The excitations at speed no load are mainly stochas tic [61,68,77,94], although the RSI excites the runner also [95,96]. As seen in Fig.…”

Section: Speed No Load and Deep Part Loadmentioning

confidence: 95%

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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Interaction between trailing edge wake and vortex rings in a Francis turbine at runaway condition: Compressible large eddy simulation

Cited by 43 publications

References 53 publications

Investigation of Pressure Fluctuation and Pulsating Hydraulic Axial Thrust in Francis Turbines

Investigation of Pressure Fluctuation and Pulsating Hydraulic Axial Thrust in Francis Turbines

Experiment on Pressure Pulsation of Axial Flow Pump System with Different Runaway Head

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

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