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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/11756
Title: Investigation of a high head Francis turbine at runaway operating conditions
Authors: Trivedi C.
Cervantes M.J.
Gandhi, Bhupendra K.
Published in: Energies
Abstract: Hydraulic turbines exhibit total load rejection during operation because of high fluctuations in the grid parameters. The generator reaches no-load instantly. Consequently, the turbine runner accelerates to high speed, runaway speed, in seconds. Under common conditions, stable runaway is only reached if after a load rejection, the control and protection mechanisms both fail and the guide vanes cannot be closed. The runner life is affected by the high amplitude pressure loading at the runaway speed. A model Francis turbine was used to investigate the consequences at the runaway condition. Measurements and simulations were performed at three operating points. The numerical simulations were performed using standard k-ε, k-ω shear stress transport (SST) and scale-adaptive simulation (SAS) models. A total of 12.8 million hexahedral mesh elements were created in the complete turbine, from the spiral casing inlet to the draft tube outlet. The experimental and numerical analysis showed that the runner was subjected to an unsteady pressure loading up to three-times the pressure loading observed at the best efficiency point. Investigates of unsteady pressure pulsations at the vaneless space, runner and draft tube are discussed in the paper. Further, unsteady swirling flow in the blade passages was observed that was rotating at a frequency of 4.8-times the runaway runner angular speed. Apart from the unsteady pressure loading, the development pattern of the swirling flow in the runner is discussed in the paper. © 2016 by the authors.
Citation: Energies (2016), 9(3): -
URI: https://doi.org/10.3390/en9030149
http://repository.iitr.ac.in/handle/123456789/11756
Issue Date: 2016
Publisher: MDPI AG
Keywords: CFD
Francis turbine
Pressure pulsation
Runaway
Runner
Transient
ISSN: 19961073
Author Scopus IDs: 55627166200
55328928400
7006087147
Author Affiliations: Trivedi, C., Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, NO-7491, Norway
Cervantes, M.J., Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, NO-7491, Norway, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, 97187, Sweden
Gandhi, B.K., Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee, 247667, India
Corresponding Author: Trivedi, C.; Department of Energy and Process Engineering, Norwegian University of Science and TechnologyNorway; email: chirag.trivedi@ntnu.no
Appears in Collections:Journal Publications [ME]

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