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Andres Müller

Cette personne a quitté l’EPFL

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Publications associées (26)

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Physical Mechanisms governing Self-Excited Pressure Oscillations in Francis Turbines

Andres Müller

The importance of renewable energy sources for the electrical power supply has grown rapidly in the past decades. Their often unpredictable nature however poses a threat to the stability of the existing electric grid. Hydroelectric powerplants play an impo ...

EPFL2014

On the physical mechanisms governing self-excited pressure surge in Francis turbines

François Avellan, Andres Müller, Christian Landry, Arthur Tristan Favrel, Keita Yamamoto

The required operating range for hydraulic machines is continually extended in an effort to integrate renewable energy sources with unsteady power outputs into the existing electrical grid. The off-design operation however brings forth unfavorable flow pat ...

IOP science2014

On the physical mechanisms governing self-excited pressure surge in Francis turbines

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

IOP Publishing2014

Experimental investigation of the mass flow gain factor in a draft tube with cavitation vortex rope

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Sébastien Alligné, Keita Yamamoto

At off-design operating operations, cavitating flow is often observed in hydraulic machines. The presence of a cavitation vortex rope may induce draft tube surge and electrical power swings at part load and full load operations. The stability analysis of t ...

2017

Experimental investigation of the local wave speed in a draft tube with cavitation vortex rope

François Avellan, Christophe Nicolet, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

Hydraulic machines operating in a wider range are subjected to cavitation developments inducing undesirable pressure pulsations which could lead to potential instability of the power plant. The occurrence of pulsating cavitation volumes in the runner and t ...

IOP Publishing Ltd2014

Hydro-acoustic resonance behavior in presence of a precessing vortex rope: observation of a lock-in phenomenon at part load Francis turbine operation

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

Francis turbines operating at part load condition experience the development of a cavitating helical vortex rope in the draft tube cone at the runner outlet. The precession movement of this vortex rope induces local convective pressure fluctuations and a s ...

IOP Publishing2014

Non-Linear Stability Analysis of a Reduced Scale Model Pump-Turbine at Off-Design Operation

François Avellan, Vlad Hasmatuchi, Andres Müller, Christian Landry, Steven Roth, Sébastien Alligné

Nowadays, the pump-storage power plants are a proven solution for storing electricity at large scale and offering flexibility to the power management. Therefore, the hydraulic machines are increasingly subject to off-design operation, start-up and shutdown ...

2011

Numerical and experimental evidence of the inter-blade cavitation vortex development at deep part load operation of a Francis turbine

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

Francis turbines are subject to various types of the cavitation flow depending on the operating condition s. In order to compensate for the stochastic nature of renewable energy sources, it is more and more required to extend the operating range of the gen ...

International Association For Hydraulic Research2016

Space and time reconstruction of the precessing vortex core in Francis turbine draft tube by 2D-PIV

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

Francis turbines operating at part load conditions experience the development of a high swirling flow at the runner outlet, giving rise to the development of a cavitation precessing vortex rope in the draft tube. The latter acts as an excitation source for ...

International Association For Hydraulic Research2016

RANS computations for identification of 1-D cavitation model parameters: application to full load cavitation vortex rope

François Avellan, Christophe Nicolet, Andres Müller, Sébastien Alligné

Due to the massive penetration of alternative renewable energies, hydropower is a key energy conversion technology for stabilizing the electrical power network by using hydraulic machines at off design operating conditions. At full load, the axisymmetric c ...

International Association For Hydraulic Research2016

Experimental method for the evaluation of the dynamic transfer matrix using pressure transducers

François Avellan, Andres Müller, Keita Yamamoto

This paper introduces an experimental method for the evaluation of dynamic transfer matrices using only pressure transducers. The discharge fluctuations are evaluated from the fluctuation of the pressure difference at different streamwise locations. The tr ...

Taylor & Francis Ltd2015

Interaction of a pulsating vortex rope with the local velocity field in a Francis turbine draft tube

François Avellan, Andres Müller, Christian Landry, Matthieu Dreyer, Arthur Tristan Favrel, Steven Roth, Alberto Bullani

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 es ...

IOP science2013

Upper part-load instability in a reduced-scale Francis turbine: an experimental study

François Avellan, Elena Vagnoni, Andres Müller, Ali Amini

Francis turbines with medium or high specific speeds may experience a particular type of instability in the upper part load in which the precessing vortex has an elliptical shape. The occurrence of the upper part-load instability (UPLI) is accompanied by l ...

SPRINGER2023

New insight in Francis turbine cavitation vortex rope: role of the runner outlet flow swirl number

François Avellan, Christophe Nicolet, Arthur Tristan Favrel, Andres Müller, Christian Landry, Joao Gomes Pereira Junior

At part load operation, Francis turbines experience the development of a cavitation vortex rope in the draft tube, whose precession acts as a pressure excitation source. In case of resonance, the resulting pressure pulsations lead to unacceptable torque an ...

Taylor & Francis Ltd2018

Dynamics of the precessing vortex rope and its interaction with the system at Francis turbines part load operating conditions

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto, Joao Gomes Pereira Junior

At part load conditions, Francis turbines experience the formation of a cavitation vortex rope at the runner outlet whose precession acts as a pressure excitation source for the hydraulic circuit. This can lead to hydro-acoustic resonances characterized by ...

2017

Hydro-acoustic resonance behavior in presence of a precessing vortex rope: observation of a lock-in phenomenon at part load Francis turbine operation

François Avellan, Arthur Tristan Favrel, Andres Müller, Christian Landry, Keita Yamamoto

IOP science2014

RANS computations for identification of 1-D cavitation model parameters: application to full load cavitation vortex rope

François Avellan, Christophe Nicolet, Andres Müller, Sébastien Alligné

2017

Special Section Proposal Tunable Devices for Modern Communications: Materials, Integration, Modeling, and Applications

Andres Müller, Andrei Müller

2018

Experimental Hydro-Mechanical Characterization of Full Load Pressure Surge in Francis Turbines

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Keita Yamamoto

Full load pressure surge limits the operating range of hydro-electric generating units by causing significant power output swings and by compromising the safety of the plant. It appears during the off-design operation of hydraulic machines, which is increa ...

2017

An experimental study on the upper part-load elliptical vortex instability in a Francis turbine

François Avellan, Elena Vagnoni, Andres Müller, Arthur Tristan Favrel, Ali Amini

This paper presents preliminary results of an experimental study on the occurrence and development of the upper part-load instability in a reduced-scale Francis turbine. The study includes draft tube pressure measurements, high-speed flow visualization, an ...

IOP Publishing2021