Numerical Prediction of Non-Cavitating and Cavitating Vortex Rope in a Francis Turbine Draft Tube
نویسندگان
چکیده
منابع مشابه
Numerical simulation of a cavitating draft tube vortex rope in a Francis turbine at part load conditions for different σ-levels
In the present study, numerical investigations of a Francis turbine at model scale are performed. A part load operating point is selected for the analysis with a focus on the cavitating draft tube vortex rope. For three σ-levels, different aspects are investigated. First, the extension of the vapor volume is analyzed and compared to high-speed visualization recordings from the measurements. Fur...
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Acoustic resonances in Francis turbines often define undesirable limitations to their operating ranges at high load. The knowledge of the mechanisms governing the onset and the sustenance of these instabilities in the swirling flow leaving the runner is essential for the development of a reliable hydroacoustic model for the prediction of system stability. The present work seeks to study experim...
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Following Stokes, several authors have studied waves with 120-degree angles at their crests caused on a free surface of fluid by the gravity force. Mathematical analysis, however, shown that similar Stokes waves can be caused by centrifugal force on surfaces where the pressure is constant, and cavitating tip vortex can be examined as a surface of an eventual appearance of axissymmetrical Stokes...
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It is well known that flow instabilities called rotating stall and surge may occur in non-cavitating turbomachines at flow rates smaller than design. Rotating stall is a local instability at the turbomachinery which is basically not dependent on the hydraulic system in which the turbomachine is installed. The stalled region rotates faster than impeller. Surge is a system instability in a hydrau...
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Draft tube of Francis type hydraulic turbine usually consists of: cone, elbow and diffuser. On the contrary, in some power stations an extra pipe should be added to the draft tube at the bottom of cone because of installation limitation. In this paper, this special case has been numerically studied. To this end CFD analysis was applied to simulate all parts of hydraulic turbine. A homogeneous m...
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ژورنال
عنوان ژورنال: Strojniški vestnik – Journal of Mechanical Engineering
سال: 2011
ISSN: 0039-2480
DOI: 10.5545/sv-jme.2010.068