Publications de Christophe Nicolet

On the prediction of the induced damage by the start-up sequence of Francis turbines: On operational resilience framework

Christophe Nicolet, Mario Paolone, Martin Seydoux, Elena Vagnoni

The number of transient operations in hydraulic machinery connected to power grid, notably start-ups and shut-downs, has observed a substantial increase in recent decades, primarily driven by the global shift toward intermittent renewable energy sources. S ...

Pergamon-Elsevier Science Ltd2024

Procedure for predicting part load resonance in Francis turbine hydropower units based on swirl number and local cavitation coefficient similitude

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Arthur Tristan Favrel, Loïc Andolfatto

Francis turbines operating at part load conditions develop a cavitation precessing vortex known as a vortex rope in the draft tube cone below the runner outlet. At part load conditions, this vortex precession acts as an excitation source inducing pressure ...

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD2019

Reduced scale model testing for prediction of eigenfrequencies and hydro-acoustic resonances in hydropower plants operating in off-design conditions

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior, Arthur Tristan Favrel

The massive penetration of the electrical network by renewable energy sources, such as wind and solar, pushes the operators to extend hydropower plant units operating range to meet the transmission system operator requirements. However, in off-design opera ...

2019

Prediction of hydro-acoustic resonances in hydropower plants by a new approach based on the concept of swirl number

François Avellan, Christophe Nicolet, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior, Arthur Tristan Favrel, Loïc Andolfatto

Hydropower plant units operating in off-design conditions are subject to cavitation flow instabilities, potentially inducing hydro-acoustic resonances under certain conditions. They can be predicted by using one-dimensional numerical models of hydropower p ...

Taylor & Francis Ltd2019

Hydropower Plants Frequency Regulation Depending on Upper Reservoir Water Level

Philippe Allenbach, Christophe Nicolet

This paper presents a novel method of hydro power plant operation, based on the control of the injectors’ or wicked gates opening time as a function of the upper reservoir level. In this way, a faster power injection, depending on the current water level o ...

2019

Renovation of hydraulic power plant: how to select the best technical options?

François Avellan, Christophe Nicolet, Christian Landry, Joao Gomes Pereira Junior, Loïc Andolfatto

With the Energy Strategy 2050, Switzerland wishes to focus on balanced utilization of hydropower potentials and new renewable energy sources to cope with nuclear energy phasing out. Integration of large amounts of new renewable energies such as wind and so ...

2018

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

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

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

Measurements of Cavitation Compliance in the Draft Tube Cone of a Reduced Scale Francis Turbine Operating at Part Load

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

Francis turbines operating at part load conditions typically experience a cavitation vortex rope immediately at the runner outlet. As the compliance of this cavitation flow is much higher than the one in cavitation-free conditions, a decrease in the value ...

2018

Prediction of Francis Turbine Prototype Part Load Pressure and Output Power Fluctuations with Hydroelectric Model

François Avellan, Christophe Nicolet, Antoine Béguin, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior

The prediction of pressure and output power fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 re ...

2017

Simulation of pump-turbine prototype fast mode transition for grid stability support

François Avellan, Christophe Nicolet, Nicolas Ruchonnet, Antoine Béguin, Olivier Braun

The paper explores the additional services that Full Size Frequency Converter, FSFC, solution can provide for the case of an existing pumped storage power plant of 2x210 MW, for which conversion from fixed speed to variable speed is investigated with a foc ...

2017

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 ...

2017

Assessment of Power Swings in Hydropower Plants Through High-Order Modeling and Eigenanalysis

Basile Kawkabani, Christophe Nicolet, Pedro Camilo de Oliveira e Silva

POWER plants are subject to introduce disturbances in the power grid, resulting from interactions with the dynamical behavior of the energy source subsystem. In the case of hydropower plants when used to compensate for variations of power generation and co ...

2017

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

Hydroelectric System Response to Part Load Vortex Rope Excitation

François Avellan, Christophe Nicolet, Antoine Béguin, Christian Landry, Sébastien Alligné, Joao Gomes Pereira Junior

The prediction of pressure and output power fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 re ...

International Association For Hydraulic Research2016

Local wave speed and bulk flow viscosity in Francis turbines at part load operation

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

The operation of Francis turbines at off-design conditions may cause the development of a cavitation vortex rope in the draft tube cone, acting as a pressure excitation source. The interactions between this excitation source and the hydraulic system at the ...

Taylor & Francis Ltd2016

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

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

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

François Avellan, Christophe Nicolet, Christian Landry, Arthur Tristan Favrel, 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

Forced response analysis of hydroelectric systems

François Avellan, Basile Kawkabani, Philippe Allenbach, Christophe Nicolet, Antoine Béguin, Sébastien Alligné, Pedro Camilo de Oliveira e Silva

At off-design operating points, Francis turbines develop cavitation vortex rope in the draft tube which may interact with the hydraulic system. Risk resonance assessment by means of eigenmodes computation of the system is usually performed. However, the sy ...

International Association For Hydraulic Research2014

Increasing Wind Power Penetration in Autonomous Power Systems through No-Flow Operation of Pelton Turbines

Basile Kawkabani, Christophe Nicolet

The integration of wind power in power systems results in a reduction in greenhouse gas emissions. Thus, it has a positive environmental impact. However, the operation of these power systems becomes increasingly complex, owing mainly to random behaviour of ...

Pergamon-Elsevier Science Ltd2014

Influence of the Hydraulic System Layout on the Stability of a Mixed Islanded Power Network

François Avellan, Christophe Nicolet, Christian Landry, Stefano Giacomini

Numerical simulation and stability analysis of an islanded power network comprising 40 MW of hydropower, 20 MW of wind power and 60 MW of gas-fired power plant are investigated. First, the modeling of each power plant is fully described. The wind farm is m ...

Springer Singapore2014