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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/12575
Title: Vortex Rope Formation in a High Head Model Francis Turbine
Authors: Goyal R.
Cervantes M.J.
Gandhi, Bhupendra K.
Published in: Journal of Fluids Engineering, Transactions of the ASME
Abstract: Francis turbine working at off-design operating condition experiences high swirling flow at the runner outlet. In the present study, a high head model Francis turbine was experimentally investigated during load rejection, i.e., best efficiency point (BEP) to part load (PL), to detect the physical mechanism that lies in the formation of vortex rope. For that, a complete measurement system of dynamic pressure, head, flow, guide vanes (GVs) angular position, and runner shaft torque was setup with corresponding sensors at selected locations of the turbine. The measurements were synchronized with the twodimensional (2D) particle image velocimetry (PIV) measurements of the draft tube. The study comprised an efficiency measurement and maximum hydraulic efficiency of 92.4±0.15% was observed at BEP condition of turbine. The severe pressure fluctuations corresponding to rotor-stator interaction (RSI), standing waves, and rotating vortex rope (RVR) have been observed in the draft tube and vaneless space of the turbine. Moreover, RVR in the draft tube has been decomposed into two different modes; rotating and plunging modes. The time of occurrence of both modes was investigated in pressure and velocity data and results showed that the plunging mode appears 0.8 s before the rotating mode. In the vaneless space, the plunging mode was captured before it appears in the draft tube. The physical mechanism behind the vortex rope formation was analyzed from the instantaneous PIV velocity vector field. The development of stagnation region at the draft tube center and high axial velocity gradients along the draft tube centerline could possibly cause the formation of vortex rope. Copyright © 2017 by ASME.
Citation: Journal of Fluids Engineering, Transactions of the ASME (2017), 139(4): -
URI: https://doi.org/10.1115/1.4035224
http://repository.iitr.ac.in/handle/123456789/12575
Issue Date: 2017
Publisher: American Society of Mechanical Engineers (ASME)
Keywords: Francis turbine
Instantaneous velocity field
Particle image velocimetry
Pressure fluctuations
Transient
Vortex rope
ISSN: 982202
Author Scopus IDs: 57191617201
55328928400
7006087147
Author Affiliations: Goyal, R., Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee, 247667, India, Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics, Lulea University of Technology, Norrbotten, 97187, Sweden
Cervantes, M.J., Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics, Lulea University of Technology, Norrbotten, 97187, Sweden, Water Power Laboratory, Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim, 7491, Norway
Gandhi, B.K., Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee, 247667, India
Corresponding Author: Gandhi, B.K.; Department of Mechanical and Industrial Engineering, Indian Institute of TechnologyIndia; email: bkgmefme@iitr.ernet.in
Appears in Collections:Journal Publications [ME]

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