Publications by Philippe Dupont

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In a centrifugal pump the interaction between the rotating impeller pressure field and the stationary diffuser pressure field yields pressure fluctuations as the result of a modulation process. These fluctuations may induce hydroacoustic pressure fluctuati ...

Regions of positive slope in the pressure-discharge characteristics can result in a reduction or even lack of damping of system instabilities. They are therefore one of the major concerns in design and operation of centrifugal pumps as they are limiting th ...

The cavitation which causes severe erosion of hydraulic machine runners is produced by the development of fixed cavities attached at the leading edge of the blades. It is clearly shown, from a comparison between the observations of cavity patterns during model tests and the damage found in the prototype, that the damaged areas of the blades extend in the wak:e of the fixed cavities. In this paper we give experimental evidence that this damage is due to the collapse of transient cavities in the fixed cavity

In centrifugal pumps, the interaction between the rotating impeller blades and the stationary diffuser vanes generates specific pressure fluctuation patterns. At off design operation, high incidence and large local pressure gradients can lead to flow separ ...

Different measurement techniques have been used to detect cavitation on a Francis turbine model. The results are compared to those obtained on the prototype and presented in the first of this series of articles. The runner mode! used for that study is built on the basis of a geometrical recovery of one of most eroded blade of the prototype. The results of the different measurements are presented and commented by comparison with prototype measurements. This comparison leads to a proposal of the physics which

An experimental study of flow in a Francis hydraulic turbine, especially designed for the GAMM Workshop, has been carried out. In order to provide a data base for the validation and comparison of computational fluid dynamics codes, a Francis turbine mode! and adequate instrumentation have been specially developed. Measurements of both global and local quantities have been performed for the best operating point of the turbine. A five-hole probe mounted on a remote traversing system provides static pressure a

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

Experimental flow analysis of hydraulic machines is of prime importance for improving the design of such a unit. Moreover, computational fluid dynamics codes need an experimental data reference in order to check their ability to simulate the main flow features. To obtain such an experimental data base a Francis turbine model and an associated instrumentation is specially developed. Measurements of both global and local quantities are performed for five different operating points of the turbine. A five-hole

The setting level of a hydraulic machine, specially for low head machines, is decided with respect to the possible alteration of the efficiency due to the cavity development. This alteration can easily be noticed by following the evolution of the efficiency 'eta' as a function of the Thoma number 'sigma' leading to the so-called 'eta'-'sigma' cavitation curves. Observation of the cavity extent in the flow passage of the runner allows to associate the drop of efficiency with a particular type of cavity devel

The setting level of a hydraulic machine, specially for low head machines, is decided with respect to the possible alteration of the efficiency due to the cavity development. This alteration can easily be noticed by plotting the evolution of the efficiency 'eta' as a function of the Thoma number 'sigma' leading to the so-called 'eta'-'sigma' cavitation curves. ln order to protect the efficiency at the best operating point against the travelling bubbles effects, the IEC norms suggest some measures relating t

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

In centrifugal pumps, the interaction between the rotating impeller and the stationary diffuser generates specific pressure fluctuation patterns. When the pump is operated at off design conditions, these pressure fluctuations increase. The resulting rise o ...

In the frame of a joint research program between EDF, Hydro Québec and IMHEF, different methods are investigated to predict cavitation erosion on Francis turbines from model. They are based on measurement of pitting, pressure fluctuations and acceleration. The measurement techniques have been detailed in Part I and Part 2. The present article describes essentially the theoretical and practical aspects of the methods and discusses the results obtained until now from the mode! and prototype tests. The first a

The influence of the cavitation level on the vortex shedding frequency is used to compare the flow field in the wake of a blunt hydrofoil, with and without hydroelastic lock-in, and with a constant Reynolds number. Accurate LOA measurements allow us to examine in detail the base flow regime considered as the excitation source of the hydroelastic phenomena. Thanks to these measurements, a second vortex street superposed on the Karman street has been observed. Comparisons between measurements and calculations

Hydraulic machine design can now take advantage of advanced flow calculation methods which are made available by several CFD software companies. Thanks to these recent developments, the so called "Volume Of Fluid" (VOF) methods can be now used for the analysis of the free surface flows in a Pelton Turbine. The aim of this paper is to evaluate this VOF approach with respect to the computation of the jet at the outlet of a Pelton injector and its trajectory in the buckets.

In the process of developing tools for cavitation erosion prediction of prototypes from mode) tests, 4 on board aggressiveness evaluation methods were tested on a severely eroded blade of a 266 MW Francis turbine. These are pressure, pit counting, DECER electrochemical and vibration measurements. All methods provided coherent results on the blade mounted measurements. The test program provided understanding of the heterogeneous erosion distribution of the prototype blades and quantitative data for compariso

Philippe Dupont

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Rotor-Stator Interaction Induced Pressure Fluctuations: CFD and Hydroacoustic Simulations in the Stationary Components of a Multistage Centrifugal Pump

Unsteady Numerical Simulations of the Flow Related to the Unstable Energy-Discharge Characteristic of a Medium Specific Speed Double Suction Pump

Cavitation erosion of the hydraulic machines : generation and dynamics of erosive cavities

Experimental Investigation of Pressure Fluctuations in a High-Energy Centrifugal Pump Stage at Off-Design Conditions

Cavitation Erosion Prediction on Francis Turbines Part 2 : Model Tests and Flow Analysis

Experimental flow study of the GAMM turbine model

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

Flow survey and blade pressure measurements in a Francis turbine model

Efficiency Alteration of Francis Turbines by travelling Bubble Cavitation

Prediction of Francis Turbines Efficiency Alteration by travelling Bubble Cavitation

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

Experimental Investigation of Flow Instabilities and Rotating Stall in a High-Energy Centrifugal Pump Stage

Cavitation Erosion Prediction on Francis Turbines Part 3 : Methodologies of Prediction

Wake flow analysis for a hydrofoil with and without hydroelastic lock-in

Flow Calculations in Pelton Turbines,- Part 2 : Free Surface Flows

Cavitation Erosion Prediction on Francis Turbines Part 1 : Measurements on the Prototype

Experimental investigation on forces due to vortex cavitation collapse for different materials

Prédiction de la cavitation liée à l'enroulement en extrêmité d'un hydrofoil de forme en plan elliptique

Three-Dimensional Flow Analysis of an Hydraulic Francis Turbine

Generation mechanism and dynamics of cavitation vortices downstream of a fixed leading edge cavity