0
research-article

U-RANS models for the simulation of full load pressure surge in Francis turbines validated by PIV

[+] Author and Article Information
Jean Decaix

University of Applied Sciences and Arts Western Switzerland, Valais, Route du Rawyl 47, 1950 Sion, Switzerland
jean.decaix@hevs.ch

Andres Müller

Laboratory for Hydraulic Machines, Ecole Polytechnique Fédérale, de Lausanne, Avenue de Cour 33 bis, 1007 Lausanne, Switzerland
andres.mueller@epfl.ch

Arthur Favrel

Laboratory for Hydraulic Machines, Ecole Polytechnique Fédérale, de Lausanne, Avenue de Cour 33 bis, 1007 Lausanne, Switzerland
arthur.favrel@epfl.ch

François Avellan

Laboratory for Hydraulic Machines, Ecole Polytechnique Fédérale, de Lausanne, Avenue de Cour 33 bis, 1007 Lausanne, Switzerland
francois.avellan@epfl.ch

Cécile Münch

University of Applied Sciences and Arts Western Switzerland, Valais, Route du Rawyl 47, 1950 Sion, Switzerland
cecile.muench@hevs.ch

1Corresponding author.

ASME doi:10.1115/1.4037278 History: Received March 01, 2017; Revised June 06, 2017

Abstract

In the course of the massive penetration of alternative renewable energies, the stabilization of the electrical power network significantly relies on the off-design operation of turbines and pump-turbines in hydropower plants. The occurrence of cavitation is however a common phenomenon at such operating conditions, often leading to critical flow instabilities which undercut the grid stabilizing capacity of the power plant. In order to predict and extend the stable operating range of hydraulic machines, a better understanding of the cavitating flows and mainly of the transition between stable and unstable flow regimes is required. In the case of Francis turbines operating at full load, an axisymmetric cavitation vortex rope develops at the runner outlet in the draft tube and enters self-oscillation, with violent periodic pressure pulsations leading to dangerous electrical power swings and mechanical vibrations. The present article reports an extensive numerical and experimental investigation on a reduced scale model of a Francis turbines at full load. For a given operating point, three pressure levels in the draft tube are considered, two of them featuring a stable flow configuration and one of them displaying a self-excited oscillation of the cavitation vortex rope. The velocity field is measured by 2-D Particle Image Velocimetry and systematically compared to the results of a simulation based on a homogeneous RANS model. The validation of the numerical approach enables a first comprehensive analysis of the flow transition as well as an attempt on explaining the onset mechanism.

Copyright (c) 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In