CNRS Institute for Aerothermal Combustion Reactivity and Environment

Orleans, France

CNRS Institute for Aerothermal Combustion Reactivity and Environment

Orleans, France

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Tsikata S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Minea T.,University Paris - Sud
Physical Review Letters | Year: 2015

The electron cyclotron drift instability, implicated in electron heating and anomalous transport, is detected in the plasma of a planar magnetron. Electron density fluctuations associated with the mode are identified via an adapted coherent Thomson scattering diagnostic, under direct current and high-power pulsed magnetron operation. Time-resolved analysis of the mode amplitude reveals that the instability, found at MHz frequencies and millimeter scales, also exhibits a kHz-scale modulation consistent with the observation of larger-scale plasma density nonuniformities, such as the rotating spoke. Sharply collimated axial fluctuations observed at the magnetron axis are consistent with the presence of escaping electrons in a region where the magnetic and electric fields are antiparallel. These results distinguish aspects of magnetron physics from other plasma sources of similar geometry, such as the Hall thruster, and broaden the scope of instabilities which may be considered to dictate magnetron plasma features. © 2015 American Physical Society.


Leroy V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Cancellieri D.,CNRS Environmental Sciences | Leoni E.,CNRS Environmental Sciences | Rossi J.-L.,CNRS Environmental Sciences
Thermochimica Acta | Year: 2010

The kinetics of thermal decomposition of a forest fuel was studied by thermogravimetry. Experiments were monitored under air and non-isothermal conditions from 400 to 900 K. We used a classical model-free method, the Kissinger-Akahira-Sunose (KAS) method to calculate the activation energy vs. the conversion degree of the reaction on the whole temperature domain. Analyses were performed at 10, 20 and 30 K/min. As expected, the complex structure of lignocellulosic fuels involved several steps with different energies in the degradation processes. The algorithm developed here, allows the calculation and the simulation of the solid temperature at different conversion degree for various heating rates. The good correlation between experiments and simulations validated the proposed algorithm. Then, kinetics parameters were used to perform simulations up to heating rates outside the functioning range of the thermal analyser. © 2009 Elsevier B.V. All rights reserved.


Gries T.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Vandenbulcke L.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Rouzaud J.N.,CNRS ENS Geology Laboratory | De Persis S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
Plasma Sources Science and Technology | Year: 2010

A decrease in electron density and a strong increase of electron energy, which induce the enhancement of excitation rates, have been observed in CH 4-CO2 plasmas when the inlet methane concentration is high enough and the input microwave power sufficiently low. Together with the decrease in the electron density with plasma duration, they are characteristic of dust formation in these plasmas. In these conditions, the formation of hydrocarbon radicals which are well known precursors of soot and the formation of first stable aromatics are reported, as observed by molecular beam mass spectrometry. Modelling of the chemistry in the plasma is carried out, which can also predict the formation of low concentrations of polyaromatic hydrocarbons. These species could be involved in the homogeneous nucleation process of carbon. As a function of the plasma duration, various carbon nanostructures are observed in the particles collected downstream of the plasma. For short durations, nanodiamond grains are formed with the size range 15-100 nm. They are composed of diamond nanocrystals of about 2-10 nm in size; these values are generally observed for all diamond nanocrystals formed in extraterrestrial and terrestrial conditions. For longer plasma durations, sp2-hybridized carbons are obtained. Their structure varies from soot to more ordered graphitic carbons nearly similar to 'onions' and structures similar to those observed in tokamaks. The control of the size and the microstructure of the nanodiamond grains are especially important as this could open possibilities for applications in a wide range of fields. © 2010 IOP Publishing Ltd.


Joussot R.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Parisse J.-D.,Aix - Marseille University
Experiments in Fluids | Year: 2015

This paper describes experimental and numerical investigations focused on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma was created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. The natural flow exhibited a shock wave with a hyperbolic shape. Pitot measurements and ICCD images of the modified flow revealed that when the discharge was ignited, the shock wave angle increased with the discharge current. The spatial distribution of the surface temperature was measured with an IR camera. The surface temperature increased with the current and decreased along the model. The temperature distribution was reproduced experimentally by placing a heating element instead of the active electrode, and numerically by modifying the boundary condition at the model surface. For the same surface temperature, experimental investigations showed that the shock wave angle was lower with the heating element than for the case with the discharge switched on. The results show that surface heating is responsible for roughly 50 % of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed. © 2015, Springer-Verlag Berlin Heidelberg.


Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2015 | Year: 2015

This investigation focuses on optical emission characterization carried out in low pressure arc-jet plasma flows applied for the investigation of radiation relevant to Mars exploration and re-entry into Earth. Experiments were performed in the plasma wind tunnel Phedra of the ICARE laboratory, equipped with an arc-jet producing low pressure and supersonic non-equilibrium plasma flows. Spectral emission from 110 nm to 900 nm, have been measured in 97% CO2-3% N2 and 80% N2-20% O2 plasmas operating with a wide range of plasma conditions in order to evaluate the contribution of VUV radiation with respect to the total one. This investigation contributes to get a set of experimental data, giving access to atmospheric entry plasma models used for predicting heat fluxes. © 2015 AIAA American Institute of Aeronautics and Astronautics. All rights reserved.


Ndiaye A.A.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
Plasma Sources Science and Technology | Year: 2011

Planetary probes penetrating at supersonic speed into high atmosphere require the development of composite materials for thermal protection of the surface exposed to a high enthalpy flux. Rarefied arc plasmas can be used to simulate the atmospheric re-entry plasmas. The aim of this paper is to describe the latest results of optical emission measurements of the CH (A-X) system, the CN violet (B-X) bands and the NH (A-X) electronic transitions in a N 2-CH4 plasma source (Titan's atmosphere) and in a gas mixture of Ar-CH4. In order to deduce the plasma parameters, such as rotational and vibrational temperatures, of these molecular species in the plasma environment, numerical simulation codes have been implemented. In this context, rotational temperatures near 7000 K for CN and 3500 K to 2800 K for the hydrides NH and CH, respectively, are observed. The vibrational temperature of the CH molecule is around 3800 K while those of the CN and NH molecules are 9500 K and 7900 K, respectively. © 2011 IOP Publishing Ltd.


Vandenbulcke L.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | De Persis S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Gries T.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Delfau J.L.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
Journal of the Taiwan Institute of Chemical Engineers | Year: 2012

The overall purpose of the present work is the feasibility study of syngas production from biogas in a microwave plasma discharge. Concentrations of both stable and labile species are presented from molecular beam mass spectrometry (MBMS) measurements in the case of a 50%CH 4-16.7%CO 2-33.3%H 2O mixture. This mixture was chosen as it leads to constant amounts of CO and H 2 (respectively 1/3:2/3) in the syngas produced if a complete conversion of the reactants is assumed. Practically, this initial mixture could be produced by any biogas provided that its composition is analyzed and completed to reach the required values. In our study, special attention is paid to the effect of microwave power (600-1600W) and pressure (10-50Torr). A complete modelling initially developed and validated (using several experimental characterization techniques such as Optical Emission Spectroscopy, Microwave Interferometry, Langmuir Probing, MBMS) for diamond deposition purposes is here used to simulate syngas production. This model takes into account the coupled hydrodynamics of the gaseous species and the gas-phase chemistry (including reactions between neutral species and dissociation by electron impact). The surface recombination of radicals at the reactor wall is also modelled. The influence of both power and pressure on syngas production is discussed as well as the transfer of the process to industry. © 2012 Taiwan Institute of Chemical Engineers.


Tsikata S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Honore C.,Ecole Polytechnique - Palaiseau | Gresillon D.,Ecole Polytechnique - Palaiseau
Journal of Instrumentation | Year: 2013

Collective (or coherent) Thomson scattering has recently emerged as an important tool for identifying and characterizing certain instabilities in Hall thrusters. Plasma instabilities in electric thrusters are implicated in diverse phenomena, including reduced efficiency, lifetime and anomalous particle transport. This work discusses the main features of the collective scattering diagnostic PRAXIS, and recent applications of the diagnostic to study the nature of microturbulence at different thruster operating regimes. Early measurements show the presence of a small-scale azimuthal instability may be linked with regimes of unstable thruster operation. © 2013 IOP Publishing Ltd and Sissa Medialab srl.


Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Joussot R.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Parisse J.-D.,Aix - Marseille University
Journal of Physics D: Applied Physics | Year: 2014

This paper describes experimental and numerical investigations focused on the shock-wave modification induced by a plasma actuator in the rarefied flow regime. The experimental investigation was carried out in the supersonic wind tunnel MARHy located at the ICARE laboratory, and the numerical investigation using a 2D fully compressible Navier-Stokes simulation was carried out at the IUSTI laboratory. The study concerns a cylinder in a Mach 2 air flow equipped with a small electrode that creates a local plasma. Electrical and optical diagnostics were used to experimentally analyse the plasma effects on the flow field. Measurements show that the shock stand-off distance increases with the discharge power. Numerical simulations show that the modification of the shock position is not induced by thermal effects. A theoretical approach is then developed in order to take into account the specific properties of plasma such as thermal non-equilibrium and ionization. It is found that the stand-off distance is directly coupled with the ionization degree of the plasma. © 2014 IOP Publishing Ltd.


Joussot R.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2016

This paper describes experimental investigations focused on the glow discharge created by a plasma actuator and used to shock wave modification over a flat plate in a Mach 2 air flow. The model is equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma is created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. ICCD images of the discharge without and with the Mach 2 flow show the influence of the flow field on the discharge morphology. In addition, ICCD images of the modified flow revealed that when the discharge is ignited, the shock wave angle increased with the applied voltage. Thermal measurements of the flat plate surface carried out with an IR camera showed that the spatial temperature distribution is not uniform along the plate and its maximum, near the leading edge, increases with the applied voltage. Previous results showed that surface heating is responsible for roughly 50% of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed. The focus of this paper is the study of the properties of the glow discharge to better understand the interaction between the supersonic flow and the purely plasma effects which are responsible of flow field modifications, in particular ionization degree and thermal disequilibrium upstream the model. © 2016 IEEE.

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