Publications de François Avellan

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The work presented in this paper details an original procedure developed in order to automatically build on-cam surfaces for double-regulated hydropower units such as Kaplan or bulb turbines. The proposed method allows a sparse exploration of the operating ...

Hydropower (HP) is the backbone of the Swiss electricity system providing around 60 % (36 TWh/a) of the total electricity generated on a yearly average. With the planned phase-out of nuclear power plants, HP and other Renewable Energy Sources (RES) will ne ...

Hydraulic turbine runners, which operate under a wide range of heads and outputs, are subjected to considerable dynamic forces at off design conditions. Therefore a detailed knowledge of mean and fluctuating pressures is required for a safe design of the runner. A special technique has been developed at EPFL-IMHEF Laboratory for Hydraulic Machines in Lausanne, Switzerland, to measure the pressures on the blade of a model runner with miniature piezo-resistive pressure transducers. It has been successfully us

This paper deals with 5-axis milling of hydraulic blades. The issue developed is essentially linked to problems due to the transition from 3 to 5 axes. A specific attention is done to the Inverse Kinematics Transformation (IKT) which can be source of incoh ...

Numerical simulation of the unsteady turbulent flow in a three-dimensional draft tube geometry is performed. The investigation is carried out with a commercial finite volume solver implementing the Reynolds averaged Navier-Stokes equations. The modeling of ...

Variable speed hydroelectric units equipped with full size frequency converter (FSFC) offer high operational flexibility enabling fast operating point transitions which increase grid regulation capacities. The XFLEX HYDRO H2020 European research project ai ...

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 ...

Erosive wear of hydraulic machines is a common issue, which results in efficiency degradation, the enhancement of cavitation, and the need for expensive maintenance. Although numerical simulations of the erosion process could be very useful, both for under ...

This paper summarizes the findings of CEA project No 307 G 657 entitled "Hydraulic Turbine Cavitation Pitting Detection by Monitoring Runner Vibration." The project was centered on the detection of leading edge cavitation, the main cause of erosion damage on Francis turbines. Based on a damage model proposed by EPFL and verified by EPFL and IREQ, the vibratory signature of erosive cavitation was first sought on a bi-dimensional NACA 009 profile in a high speed cavitation tunnel and then on the model and the

The aim of this paper is to present the results obtained with a 3-D numerical method allowing the prediction of the cavitation behaviour of a centrifugal pump and to compare this prediction to model tests. The proposed method consists in assuming the cavity interface as a free surface boundary of the computation domain and in computing the single phase flow. The unknown shape of the interface is predicted by an iterative procedure matching the cavity surface to a constant pressure boundary (pv). The origina

Hydropower plants may be required to operate in synchronous condenser mode in order to supply reactive power to the grid for compensating the fluctuations introduced by the intermittent renewable energies such wind and solar. When operating in this mode, t ...

In a conventional design and manufacturing process, turbine blades are modeled based on reverse engineering or on parametric modeling with Computer Fluids Dynamics (CFD) optimization. Then, only raises the question of the manufacturing of the blades. As th ...

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 flow in the draft tube cone of Francis turbines operated at partial discharge is a complex hydrodynamic phenomenon where an incoming steady axisymmetric swirling flow evolves into a three-dimensional unsteady flow field with precessing helical vortex ( ...

Dredge pumps are usually operated at part-load conditions, in which the low-solidity centrifugal impeller could experience large internal energy dissipation, related to flow separation and vortices. In this study, SST k- and SAS-SST turbulence models were ...

The transient behavior of hydroelectric power plants is of high interest for ensuring stability of islanded electrical power networks. Therefore, it is suitable to determine and validate the set of parameters of a turbine speed governor using a realistic s ...

The objective of the present paper is to perform numerical simulations of a high-speed water jet impinging on rotating Pelton buckets using the finite volume particle method (FVPM), which combines attractive features of smoothed particle hydrodynamics (SPH ...

A swirling wake flow submitted to an adverse pressure gradient is studied by bifurcation analysis, modal analysis and direct numerical simulations. In contrast to experiments in diverging tubes, the adverse pressure gradient is imposed by the presence of a ...

Pumped storage power plants are key components for the development of new renewable CO2-free primary energies and the security enhancement of electricity supply. They also offer interesting business opportunities in nowadays liberalized electricity market. ...

Many different types of branching have been developed, such as bifurcation, trifurcation, and manifolds, among others. These configurations are used in penstocks to transport water from surge tanks to power houses in order to feed several turbines at the s ...

François Avellan

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Automated hill chart modeling procedure to estimate the performance of double regulated units

Swiss Potential for Hydropower Generation and Storage - Synthesis report

Dynamic Pressure Measurements on a Model Turbine Runner and their Use in Preventing Runner Fatigue Failure

Tool Path Generation and Post-Processor Issues in Five-Axis High Speed Machining of Hydro Turbine Blades

Flow Simulation in an Elbow Diffuser : Verification and Validation

Turbine mode start-up simulation of a FSFC variable speed pump-turbine prototype - Part I: 1D simulation

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

Multiscale Simulation of the Hydroabrasive Erosion of a Pelton Bucket: Bridging Scales to Improve the Accuracy

Erosion vibratory fingerprint of leading edge cavitation of a NACA profile and of a Francis model and prototype hydroturbine

Leading edge cavitation in a centrifugal pump : numerical predictions compared with model tests

On the sloshing free surface in the draft tube cone of a Francis turbine operating in synchronous condenser mode

Design optimization of a 2D blade by means of milling tool path

Cavitation surge modelling in Francis turbine draft tube

Axisymmetric swirling flow simulation of the draft tube vortex in Francis turbines at partial discharge

Unsteady Flow Numerical Simulations on Internal Energy Dissipation for a Low-Head Centrifugal Pump at Part-Load Operating Conditions

Turbine Speed Governor Parameters Validation in Islanded Production

Flow Simulation of Jet Deviation by Rotating Pelton Buckets Using Finite Volume Particle Method

Vortex impingement onto an axisymmetric obstacle - subcritical bifurcation to vortex breakdown

Experimental investigation of a pump-turbine at off-design operating conditions

Numerical analysis for detecting head losses in trifurcations of high head in hydropower plants