Interaction of a pulsating vortex rope with the local velocity field in a Francis turbine draft tube
Year: 2012
Type: conference-paper
Abstract: 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 experimentally the unstable draft tube flow by conducting a series of measurements on a reduced Francis Turbine model. The key physical parameters and their interaction with the hydraulic and mechanical system are studied and quantified. In particular, the evolution of the axial and tangential velocity components in the draft tube cone is analysed by means of Laser Doppler Anemometry. Combined with the calculation of the instantaneous vortex rope volume based on flow visualization and the measurement of the pressure fluctuations, the nature of the auto-oscillation in the draft tube flow is investigated.
Authors: A Müller, A Bullani, M Dreyer, S Roth, A Favrel, C Landry, F Avellan
Institution: École Polytechnique Fédérale de Lausanne
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2136253129