Concept

Tube map

Related publications (15)

STABILITY OF TURBINE DRAFT TUBE VORTEX

For a given specific energy in hydraulic machines, there is a peak efficiency at a certain flow rate, known as the Best Efficiency Point (BEP). Beyond this point, efficiency decreases in an almost quadratic manner as flow rate deviates. This study aims to establish a connection between this phenomenon and the flow stability properties at two different operating points. The base flow vortex considered here is based on the experimental data by [1, 2]. Based on experimental measurement at a location of turbine

2025

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

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

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

Cavitation surge modelling in Francis turbine draft tube

François Avellan

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

Taylor & Francis Ltd2014

What Future for the Urban Underground? Subsurface and Surface Potential in San Antonio, Texas

The Deep City project at the École polytechnique fédérale de Lausanne has, for the past several years, been developing a method to identify and qualify the urban areas where underground development is high, particularly for human activities. The fourth dissertation to contribute to this project, begun by the author in 2012, seeks to combine morphological and topological properties of the surface with the hydrogeological characteristics of the underground in order to develop strategies to integrate future un

2014

Identification and Modeling of Pressure Fluctuations of a Francis Turbine Scale Model at Part Load Operation

François Avellan

Scale model of high specific speed Francis turbines may present at upper part load operation under low cavitation number pressure fluctuation in the range 2 to 4 times fn, the rotating frequency. In the framework of the FLINDT project, pressure measurements on the draft tube wall of a Francis turbine scale model at 104 locations revealed such phenomenon at a frequency of almost 2.5 fn. The phase shift analysis of the measured pressure fluctuations in the draft tube at this frequency points out a pressure so

International Association For Hydraulic Research2004

Analyse du champ de pression pariétale d'un diffuseur coudé de turbine Francis

Jorge Alejandro Arpe Alca

At this time, a large number of hydraulic turbomachinery installations are ageing, so that they need refurbishement to increase their efficiency and their associated output power. The items that need refurbishement are mainly the runner and the guide vanes. The draft tube and the spiral casing are generally not modified, for cost and safety reasons. An unsuitable match between the new runner and the old draft tube can lead to an unfavourable flow behavior and an efficiency drop when the hydroelectric plant

EPFL2003

Field Assessment of Cavitation Detection Methods in Hydropower Plants

François Avellan, Mohamed Farhat

An experimental investigation on Francis turbines suffering from inlet cavitation erosion on the runner blades has permitted to assess several aspects of the actual cavitation erosion detection and prediction methods based on vibrations. Detection tests in three prototypes have consisted in the measurement of vibrations in turbine guide bearing, guide vanes and draft tube during operation. Discussion about RMS levels, auto power spectra and amplitude demodulation results is provided. A dynamic calibration h

International Association For Hydraulic Research2002

Numerical simulation and flow analysis of an elbow diffuser

Sebastiano Mauri

Numerical simulation of the unsteady turbulent flow in a three-dimensional elbow diffuser is performed. The investigation is carried out with a commercial finite volume solver implementing the Reynolds averaged Navier-Stokes equations. Against the background of current research in DNS and LES, the modeling of most practically relevant turbulent flows continues to be based on this system of equations. For this reason it is important to evaluate the limitations of the Reynolds averaging approach with the asso

EPFL2002

Flow Investigation in a Francis Draft Tube : the Flindt Project

François Avellan

The flow investigation in a elbow draft tube is presented. After a review of the existing works related to the flow analysis of such component, the need of an experimental validation of the CFD tools is discussed with respect the practical interest of improving the matching of a runner and the draft tube. The geometry and the main characteristics of the test model is described and the pressure recovery coefficient is provided in an extended operating range. The instrumentation of the draft tube and the LDA

International Association For Hydraulic Research2000

Unstable Part-Load Operation of a Model Francis Turbine : Evaluation of Disturbance Magnitude

The low frequency pressure oscillations observed at the draft tube wall of a Francis turbine operating at part load may be split into two uniform components: a rotating pressure with a constant area-averaged value, and a synchronous pulse involving the whole draft tube section. The synchronous pulse is sometimes used to evaluate the magnitude of disturbances generated by part-load operation of the turbine. A more global way to evaluate the magnitude of these disturbances is to estimate the emission of acous

International Association For Hydraulic Research1994

Comparison of Flow Computation Results with experimental Flow Surveys in a Francis Turbine

François Avellan, Philippe Dupont, Etienne Parkinson

Three dimensional numerical tools are now commonly used in the design or analysis process of the internai flow of hydraulic machinery. As an illustration of the use of such tools to study the internai flow of a Francis turbine, the computational results obtained in all components of this turbine with an Euler equations solver and two Reynolds Averaged Navier Stokes equations solvers are discussed. The analysis process is illustrated and comparisons with experimental results obtained in the spiral casing and

International Association For Hydraulic Research1994

A characterization procedure for the dynamic behavior of Francis turbines : Practical comparison of elbow and Moody type draft tubes

Characterization from model tests of the dynamic behavior of hydraulic turbines operating off design conditions is an important step in the knowledge of instability phenomena. IMHEF at EPF-Lausanne, Switzerland meets this purpose with a standard test procedure . Simple , fast and efficient, it yields complete and easily interpreted results. This test procedure is used here to compare the dynamic characteristics of elbow and Moody type draft tubes . Relevant frequencies and cavitation compliance are expresse

International Association For Hydraulic Research1988

Scale effect concerning hydraulic quasi-stationary oscillations on a turbine model and test circuit

For the continuation of the study undertaken during the Amsterdam Symposium and within the framework of the "Work Group on the Behavior of Hydraulic Machinery under steady oscillatory conditions" the authors have the following objectives: - comparison between the experimental responses of the circuit to a piston machine excitation and the calculated responses by the impedance method; - comparison between the experimental responses of the circuit to a piston machine excitation and the responses to excitation

International Association For Hydraulic Research1984

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Related publications (15)

A characterization procedure for the dynamic behavior of Francis turbines : Practical comparison of elbow and Moody type draft tubes

International Association For Hydraulic Research1988

Scale effect concerning hydraulic quasi-stationary oscillations on a turbine model and test circuit

International Association For Hydraulic Research1984