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D. Rochette

Université Blaise-Pascal, F- Clermont-Ferrand, IUT d'Allier, Faculty Member

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Papers by D. Rochette

Numerical simulation of a pressure wave interacting with a protection filter during an internal arc fault in a medium voltage cell

by William Bussière, D. Rochette, and Andre Pascal

We present a two-dimensional mathematical model and a specific numerical method to study the inte... more We present a two-dimensional mathematical model and a specific numerical method to study the interaction of a pressure shock wave, due to an internal arc fault, with a protection filter in a medium voltage cell. The model is based on Euler equations in porous medium taking into account the porosity variation. Calculation results are compared to experimental measurements of the pressure performed on apparatus specially adapted for tests.

Measurement of the pre-arcing time and the fulgurite length in hbc fuse in the case of tests performed with an A.C. 100 KVA station

by William Bussière, D. Rochette, and Andre Pascal

2007 8th International Conference on Electric Fuses and their Applications, 2007

This study deals with a specific test device especially designed to perform tests on HBC fuse on ... more This study deals with a specific test device especially designed to perform tests on HBC fuse on a scale of a non industrial laboratory. In fact it is not possible for most of academic laboratories to build up a device supplying the same current and voltage ranges as in an industrial test station. Moreover the capacitor bank discharges are often used in academic laboratories to test electric fuses. But the main drawback of the capacitor bank is to supply a non 50 Hz-sinusoidal current waveform for one half period only. We present the first measurements performed on experimental HBC fuses using a 100 kVA station built up from a single phase transformer. These first measurements are performed using various fuse elements with the same geometries as in industrial fuses of the middle voltage range. The filling material is silica sand or quartz sand and it is chosen with the same properties as in industrial fuses. The fuse working is studied experimentally on the whole duration of the fuse working which depends on the values chosen for the power factor and the closing angle. The results are given for the pre-arcing time and the fulgurite length. The power factor put in the tests is equal to 9 . 0 cosϕ and 1 . 0 cosϕ , and the closing angle is increased from 0 ° to 180 °. The results are discussed by taking into account the influence of the energy to dissipate, namely the Joule energy and the inductive energy.

First Step in Theoretical Approach in Study of Mars and Titan Atmospheres with an Inductively Coupled Plasma Torch

by Rachid Touzani, M. Dudeck, Andre Pascal, and D. Rochette

To obtain the modelling of an ICP torch that can be used as a test case, we have to determine all... more To obtain the modelling of an ICP torch that can be used as a test case, we have to determine all the thermodynamic properties and transport coefficients. To calculate the data we have first to determine the composition and the collisions integrals for all the species in the purpose to calculate the transport coefficients. We apply the calculation to the Mars and to the Titan atmosphere compositions. The intensities of the spectral lines are determined versus temperature.    e J J t i t i e J e z r, z r,

Multislope MUSCL method for unstructured meshes applied to the compressible axisymmetric Euler equations for swirling flows

by Rachid Touzani and D. Rochette

Journal of Computational Physics, Jul 1, 2010

A finite volume method for the numerical solution of axisymmetric inviscid swirling flows is pre... more A finite volume method for the numerical solution of axisymmetric inviscid swirling flows
is presented. The governing equations of the flow are the axisymmetric compressible Euler
equations including swirl (or tangential) velocity. A first-order scheme is introduced where
the convective fluxes at cell interfaces are evaluated by the Rusanov or the HLLC numerical
flux while the geometric source terms are discretizated to provide a well-balanced scheme
i.e. the steady-state solutions with null velocity are preserved. Extension to the secondorder
space approximation using a multislope MUSCL method is then derived. To test
the numerical scheme, a stationary solution of the fluid flow following the radial direction
has been established with a zero and nonzero tangential velocity. Numerical and exact
solutions are compared for classical Riemann problems where we employ different limiters
and effectiveness of the multislope MUSCL scheme is demonstrated for strongly shocked
axially symmetric flows like in spherical bubble compression problem. Two other tests
with axisymmetric geometries are performed: the supersonic flow in a tube with a cone
and the axisymmetric blunt body with a free stream.

Numerical study of the short pre-arcing time in high breaking capacity fuses via an enthalpy formulation

by Rachid Touzani, William Bussière, and D. Rochette

Journal of Physics D-applied Physics, 2007

In order to study the short pre-arcing time in high breaking capacity (HBC) fuses, we use a mathe... more In order to study the short pre-arcing time in high breaking capacity (HBC) fuses, we use a mathematical model including the phase change of the fuse-element heating coupled with the Laplace equation for the potential and Ohm's law. The thermal model is based on the enthalpy formulation of the heat equation with a source term representing the Joule heating. For the time range considered (up to 10 ms), we assume no heat transfer between the fuse-element and the surrounding sand. To solve numerically the governing equations, we employ a semi-implicit scheme for time integration and a finite element method for space discretization. Using electrical and thermal properties of the silver fuse-element, we present pre-arcing characteristics (temperature, current density, potential) for a fuse-element used in industrial protection circuits.

Modelling of the pre-arcing period in HBC fuses including solid - liquid - vapour phase changes of the fuse element

by Rachid Touzani, William Bussière, Andre Pascal, and D. Rochette

In this paper, we present a model and a numerical method of the fuse element heating including so... more In this paper, we present a model and a numerical method of the fuse element heating including solid -liquid -vapour phase transitions in order to evaluate the pre-arcing time in HBC fuses. The mathematical model is based on the enthalpy formulation of the heat equation with a source term representing the Joule effect coupled with the Laplace equation for the potential and the Ohm's law. We obtain an approximation of the governing equations using a specific numerical scheme for time discretization and unstructured triangle or tetrahedral element grids are employed in spatial discretization using a standard piecewise linear finite element method. Numerical simulations of two fuse elements, used in industrial applications, are carried out and compared with experimental measurements obtained using a 100 kVA power station.

Numerical study of the short pre-arcing time in high breaking capacity fuses via an enthalpy formulation

by William Bussière, Rachid Touzani, and D. Rochette

Journal of Physics D: Applied Physics, 2007

In order to study the short pre-arcing time in high breaking capacity (HBC) fuses, we use a mathe... more In order to study the short pre-arcing time in high breaking capacity (HBC) fuses, we use a mathematical model including the phase change of the fuse-element heating coupled with the Laplace equation for the potential and Ohm's law. The thermal model is based on the enthalpy formulation of the heat equation with a source term representing the Joule heating. For the time range considered (up to 10 ms), we assume no heat transfer between the fuse-element and the surrounding sand. To solve numerically the governing equations, we employ a semi-implicit scheme for time integration and a finite element method for space discretization. Using electrical and thermal properties of the silver fuse-element, we present pre-arcing characteristics (temperature, current density, potential) for a fuse-element used in industrial protection circuits.

Modelling of the pre-arcing period in HBC fuses including solid - liquid - vapour phase changes of the fuse element

by D. Rochette and William Bussière

2007 8th International Conference on Electric Fuses and their Applications, 2007

In this paper, we present a model and a numerical method of the fuse element heating including so... more In this paper, we present a model and a numerical method of the fuse element heating including solid -liquid -vapour phase transitions in order to evaluate the pre-arcing time in HBC fuses. The mathematical model is based on the enthalpy formulation of the heat equation with a source term representing the Joule effect coupled with the Laplace equation for the potential and the Ohm's law. We obtain an approximation of the governing equations using a specific numerical scheme for time discretization and unstructured triangle or tetrahedral element grids are employed in spatial discretization using a standard piecewise linear finite element method. Numerical simulations of two fuse elements, used in industrial applications, are carried out and compared with experimental measurements obtained using a 100 kVA power station.

Pre-Arcing Times in HBC Fuse for High Fault Currents. Comparison Between Simulation and Experiment

by D. Rochette, Andre Pascal, and William Bussière

High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2008

This work deals with the calculation of pre-arcing time in the case of High Breaking Capacity fus... more This work deals with the calculation of pre-arcing time in the case of High Breaking Capacity fuses submitted to high fault currents&quot; The fuse elements studied consist of silver fuse strips with reduced sections in their centre. During the fuse working the fuse element is fused partly and hence vaporized. The time necessary to obtain an electric arc is called the pre-arcing time. This latter is defined by the duration from the appearance of the fault cunent to the splitting of the fuse element due to the vaporization of the reduced sections. The mathematic model is based on the solution of the heat transfer Eq., using an en-thalpy forrnulation to take into account the phase transitions, supplemented by an energy source due to the heat produced by ohrnic losses. In order to determine the current density evolution in the fuse element, the l-aplace Eq. goveming the electric potential and the Ohm&#39;s larv are used. Two typical fuse elements close to industrial ones are chosen for the simulations. The calculated pre-arcing times are given together with the main electrical properties, and compared with the experimental values. The resistive case withcos ç-0.9 is discussed for a 2.5 mm and 7.5 mm-width elements respectively with one and three reduced sections.

Simulations and Measurements of the Pre-Arcing Times in HBC Fuses Under Typical Electric Faults

by D. Rochette and William Bussière

High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2010

This work deals with the comparison between calculations and measurements of pre-arcing times in ... more This work deals with the comparison between calculations and measurements of pre-arcing times in High Breaking Capacity fuses under typical fault current conditions. This paper also describes the temperature evolution and the Joule energy dissipated in a fuse element during the pre-arcing time. By varying typical electrical parameters, namely the closing angle and the power factor, we show that various prospective currents such as those observed in industrial case can be fairly simulated. The pre-arcing time and then the clearing of the fault current are shown to be deeply dependent on these electrical characteristics. We exhibit simulated results of prospective current and supply voltage waves for given closing angles under two typical power factors which are compared with the experimental ones. A comparison between simulated pre-arcing times with experimental ones shows some discrepancies and a discussion on the numerical assumptions is made.

Numerical method for pre-arcing times: Application in HBC fuses with heavy fault-currents

by D. Rochette and William Bussière

2007 8th International Conference on Electric Fuses and their Applications, 2007

ABSTRACT This works deals with calculations of pre-arcing time prediction for fuse links used in ... more ABSTRACT This works deals with calculations of pre-arcing time prediction for fuse links used in industrial protection circuits in case of heavy faults-currents. An enthalpy method to solve heat-transfer equation included two phase-changes is presented. The mathematical model couples thermal and electrical equations based on the principle of energy conservation and the Ohm&#39;s law respectively. In order to determine current density and temperature evolution in the fuses, three typical fuse links have been chosen for the calculations with circular, rectangular and trapezoidal reduced sections at their centre. Silver physical properties, mathematical equations and the numerical method are reported. Calculations results show that for the fuse link with rectangular reduced section a major heat-transfer mechanism took place compared to the other ones.

Basic data: Composition, thermodynamic properties and transport coefficients applied to fuses

by D. Rochette and William Bussière

2007 8th International Conference on Electric Fuses and their Applications, 2007

Two main areas of research can be determined for the basic data that are composition, thermodynam... more Two main areas of research can be determined for the basic data that are composition, thermodynamic properties and transport coefficients: the polyphasic area and the gas phase and plasma phase area. In the case of mixture of (Ag, SiO 2 ) that can be found in fuses field, we depict the main results available at the present time.

Measurement of Darcy and Forchheimer Coefficients for Silica Sand Beads

by D. Rochette and William Bussière

High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2006

High Breaking Capacity fuses are widely used to withdraw the energy brought by an electric fault ... more High Breaking Capacity fuses are widely used to withdraw the energy brought by an electric fault current. One of the main constituent elements of a HBC fuse is the arc quenching material, silica sand in our case. During the arc quenching by the fuse, a plasma is generated due to the firsion and the vaporization of the fuse element (Ag) and the silica sand (SiO2). The plasma resulting from the dissociation of Ag and SiOz is surrounded by a fused silica viscous sheath itself surrounded by silica sand grains. In this study it is showed that the main silica sand morphometric propertiesgranulometry, porosity, Darcy and Forchheimer coefficients -shongly influence the fuse operation. The measurements of the Darcy and Forcbheimer coefficients are described, and the results are given for silica sand beads and glass sphere 55 HIGH TEMPERATURE MATERIAL PROCESSES beads. The ir:fluence of the morphometric properties is discussed taking into consideration already published data concenring pressure, temperature and electron density of the plasma generated during the fuse operation.

Numerical simulation of Darcy and Forchheimer force distribution in a HBC fuse

We present the breaking of a short-circuit current in a HBC fuse simulation based on an isentropi... more We present the breaking of a short-circuit current in a HBC fuse simulation based on an isentropic non-stationary model in a porous medium for a one dimensional geometry. The fluid flow is affected by the nature of the gas and by the morphology of the silica sand. To model the gas-silica sand interaction, we introduce two classical laws: the Darcy's law due to the viscous interaction and the Forchheimer's law due to the inertial force. Numerical simulations with realistic physical parameters have been performed using a finite volume scheme with a fractional step technique. We show the evolution of Darcy and Forchheimer forces during time and according to the position in the fuse. We place in prominent position the fact that either force is predominant in the fuse according to the time and the position which justifies a numerical treatment to cover all the situations.

Contributions to numerical developments in shock waves attenuation in porous filters

Shock Waves, 2007

The paper deals with the numerical method of the compressible gas flow through a porous filter em... more The paper deals with the numerical method of the compressible gas flow through a porous filter emphasizing the treatment of the interface between a pure gaseous phase and a solid phase. An incident shock wave is initiated in the gaseous phase interacting with a porous filter inducing a transmitted and a reflected wave. To take into account the discontinuity jump in the porosity between the gaseous phase and the porous filter, an approximate Riemann solver is used to compute homogeneous non-conservative Euler equations in porous media using ideal gas state law. The discretization of this problem is based on a finite volume method where the fluxes are evaluated by a "volumes finis Roe" (VFRoe) scheme. A stationary solution is determined with a continuous variable porosity in order to test the numerical scheme. Numerical results are compared with the two-phase shock tube experiments and simulations of a shock wave attenuation and gas filtration in porous filters are presented.

Pressure evolution during HBC fuse operation

by D. Rochette and William Bussière

Plasma Sources Science and Technology, 2004

The purpose of this paper is to describe the influence of the silica sand grains on pressure duri... more The purpose of this paper is to describe the influence of the silica sand grains on pressure during the energy release in a high breaking capacity (HBC) fuse. During the HBC fuse operation, the pressure evolution is the result of two opposite trends: the pressure increase due to the interaction of the silica plasma with the surrounding granular sand, and

Plasma Formed in Argon, Acid Nitric and Water Used in Industrial ICP Torches

by D. Rochette and M. Benbakkar

Plasma Science and Technology, 2012

Inductively coupled plasmas (ICPs) are used in spectrochemical analyses. The introduction of the ... more Inductively coupled plasmas (ICPs) are used in spectrochemical analyses. The introduction of the sample by means of an aerosol are widely used. The introduction and the total evaporation of the aerosol is required in order to obtain a good repeatability and reproducibility of analyses. To check whether the vaporization of the aerosol droplets inside the plasma is completed, a solution could be used to compare the experimental results of the emission spectral lines with theoretical results. An accurate calculation code to obtain monatomic spectral lines intensities is therefore required, which is the purpose of the present paper. The mixtures of argon, water and nitric acid are widely used in spectrochemical analyses with ICPs. With these mixtures, we calculate the composition, thermodynamic functions and monatomic spectral lines intensities of the plasma at thermodynamic equilibrium and at atmospheric pressure. To obtain a self sufficient paper and also to allow other researchers to compare their results, all required data and a robust accurate algorithm, which is simple and easy to compute, are given.

Composition, Enthalpy, and Vaporization Temperature Calculation of Ag?SiO2 Plasmas with Air in the Temperature Range from 1000 to 6000�K and for Pressure Included between 1 and 50 bars

by D. Rochette and William Bussière

Plasma Chemistry and Plasma Processing, 2004

Experimental study of HBC fuses working at short and medium pre-arcing times

by D. Rochette and William Bussière

Journal of Physics D: Applied Physics, 2008

Pre-arcing stage is the first working step in high breaking capacity (HBC) fuse operation and aff... more Pre-arcing stage is the first working step in high breaking capacity (HBC) fuse operation and affects the following step, namely, the arcing step. We have performed realistic HBC fuse tests for short (<10 ms) and medium (>10 ms) pre-arcing times by varying the phase angle of the electrical fault (defined as the phase angle of the fault current once the supplied voltage is applied to the fuse) in the range from 0 • to 160 • , for two values of the power factor (cos ϕ ∼ 0.9 and cos ϕ ∼ 0.1). Experimental values of the pre-arcing time and the arcing time (t arc ) are given for t prearc /t arc 1 to ∼4.2, and discussed from the energetic point of view by taking into account the inductive source term. The adiabatic assumption classically used in the modelling is also examined. The influence of the pre-arcing step on the arcing step is analysed by means of the Joule integral, the energy dissipated in the fuse and the mass and length of the fulgurite.

First- and second-order finite volume methods for the one-dimensional nonconservative Euler system

Journal of Computational Physics, 2009

Gas flow in porous media with a nonconstant porosity function provides a nonconservative Euler sy... more Gas flow in porous media with a nonconstant porosity function provides a nonconservative Euler system. We propose a new class of schemes for such a system for the one-dimensional situations based on nonconservative fluxes preserving the steady-state solutions. We derive a second-order scheme using a splitting of the porosity function into a discontinuous and a regular part where the regular part is treated as a source term while the discontinuous part is treated with the nonconservative fluxes. We then present a classification of all the configurations for the Riemann problem solutions. In particularly, we carefully study the resonant situations when two eigenvalues are superposed. Based on the classification, we deal with the inverse Riemann problem and present algorithms to compute the exact solutions. We finally propose new Sod problems to test the schemes for the resonant situations where numerical simulations are performed to compare with the theoretical solutions. The schemes accuracy (first-and second-order) is evaluated comparing with a nontrivial steady-state solution with the numerical approximation and convergence curves are established.