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Open AccessArticle

Numerical Study of a Francis Turbine over Wide Operating Range: Some Practical Aspects of Verification

Waterpower Laboratory, NTNU—Norwegian University of Science and Technology, 7491 Trondheim, Norway
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Author to whom correspondence should be addressed.
Current address: Design Engineer, Rainpower Norge AS, Norway.
Academic Editor: Emanuele Quaranta
Sustainability 2020, 12(10), 4301; https://doi.org/10.3390/su12104301
Received: 7 January 2020 / Revised: 2 May 2020 / Accepted: 22 May 2020 / Published: 25 May 2020
Hydropower plays an essential role in maintaining energy flexibility. Modern designs focus on sustainability and robustness using different numerical tools. Automatic optimization of the turbines is widely used, including low, mini and micro head turbines. The numerical techniques are not always foolproof in the absence of experimental data, and hence accurate verification is a key component of automatic optimization processes. This work aims to investigate the newly designed Francis runner for flexible operation. Unsteady simulations at 80 operating points of the turbine were conducted. The numerical model consisted of 16 million nodes of hexahedral mesh. A SAS-SST (scale adaptive simulation-shear stress transport) model was enabled for resolving/modeling the turbulent flow. The selected time-step size was equivalent to one-degree angular rotation of the runner. Global parameters, such as efficiency, torque, head and flow rate were considered for proper verification and validation. (1) A complete hill diagram of the turbine was prepared and verified with the reference case. (2) The relative error in hydraulic efficiency was computed and the over trend was studied. This allowed us to investigate the consistency of the numerical model under extreme operating conditions, far away from the best efficiency point. (3) Unsteady fluctuations of runner output torque were studied to identify unstable regions and magnitude of torque oscillations. View Full-Text
Keywords: cfd; energy; Francis turbine; hydropower; verification cfd; energy; Francis turbine; hydropower; verification
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Trivedi, C.; Iliev, I.; Dahlhaug, O.G. Numerical Study of a Francis Turbine over Wide Operating Range: Some Practical Aspects of Verification. Sustainability 2020, 12, 4301.

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