Cavitation surge modelling in Francis turbine draft tube

Francis turbines may experience cavitation surge phenomenon in the draft tube inducing large pressure fluctuations which can jeopardize the hydraulic system integrity. To predict this phenomenon, a one-dimensional draft tube model is derived from flow momentum and continuity equations including the convective terms that are not considered in the existing models. A parametric analysis of the draft tube model is carried out to investigate the influence of parameters on the cavitation surge onset identified by the hydraulic system stability. It is shown that convective terms have a stabilizing influence modifying stability limit prediction driven by the divergent geometry modelling of the draft tube.

[1]  Christopher E. Brennen,et al.  The Dynamic Transfer Function for a Cavitating Inducer , 1976 .

[2]  E. Benjamin Wylie,et al.  Fluid Transients in Systems , 1993 .

[3]  Andres Müller,et al.  Draft tube discharge fluctuation during self-sustained pressure surge: fluorescent particle image velocimetry in two-phase flow , 2013 .

[4]  François Avellan,et al.  Identification of Francis Turbine Helical Vortex Rope Excitation by CFD and Resonance Simulation With the Hydraulic System , 2011 .

[5]  Christopher E. Brennen.  Bubbly flow model for the dynamic characteristics of cavitating pumps , 1978 .

[6]  Mark E. Duttweiler,et al.  Surge instability on a cavitating propeller , 2001, Journal of Fluid Mechanics.

[7]  Jean Eustache Prenat,et al.  High load behaviour of a Francis turbine model and scale effects , 1986 .

[8]  Christophe Nicolet,et al.  Hydroacoustic modelling and numerical simulation of unsteady operation of hydroelectric systems , 2007 .

[9]  P. Doerfler.  Francis Turbine Surge Prediction and Prevention , 1986 .

[10]  Yoshinobu Tsujimoto,et al.  Cavitation Surge in a Small Model Test Facility Simulating a Hydraulic Power Plant , 2012 .

[11]  Yoshinobu Tsujimoto,et al.  One-Dimensional Analysis of Full Load Draft Tube Surge , 2007 .

[12]  F. Avellan,et al.  Experimental Evidence of Hydroacoustic Pressure Waves in a Francis Turbine Elbow Draft Tube for Low Discharge Conditions , 2009 .

[13]  Christophe Nicolet,et al.  Methodology for Risk Assessment of Part Load Resonance in Francis Turbine Power Plant , 2006 .

[14]  Jean Eustache Prenat,et al.  Surging of 140 MW Francis turbines at high load, analysis and solution , 1992 .

[15]  Sébastien Alligné,et al.  Prediction of a Francis turbine prototype full load instability from investigations on the reduced scale model , 2010 .

[16]  P K Dörfler,et al.  Francis full-load surge mechanism identified by unsteady 2-phase CFD , 2010 .

[17]  Christophe Nicolet,et al.  Overload Surge Event in a Pumped-Storage Power Plant , 2006 .

[18]  Alain Sapin.  Logiciel modulaire pour la simulation et l"étude des systèmes d"entraînement et des réseaux électriques , 1995 .

[19]  Christophe Nicolet,et al.  Influence of the Francis turbine location under vortex rope excitation on the hydraulic system stability , 2009 .

[20]  Giuseppe Pezzinga,et al.  Second viscosity in transient cavitating pipe flows , 2003 .

[21]  Christophe Nicolet,et al.  Modeling of unsteady friction and viscoelastic damping in piping systems , 2012 .

[22]  Jean Eustache Prenat,et al.  Comportement dynamique d'une turbine Francis à forte charge. Comparaisons modèle-prototype , 1988 .