CNRS Institute for Aerothermal Combustion Reactivity and Environment

Orleans, France

CNRS Institute for Aerothermal Combustion Reactivity and Environment

Orleans, France
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Coumar S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Lago V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
Experiments in Fluids | Year: 2017

This paper presents an experimental investigation, carried out at the Icare Laboratory by the FAST team, focusing on plasma flow control in supersonic and rarefied regime. The study analyzes how the Mach number as well as the ambient pressure modify the repercussions of the plasma actuator on the shock wave. It follows previous experiments performed in the MARHy (ex–SR3) wind tunnel with a Mach 2 flow interacting with a sharp flat plate, where modifications induced by a plasma actuator were observed. The flat plate was equipped with a plasma actuator composed of two aluminum electrodes. The upstream one was biased with a negative DC potential and thus, created a glow discharge type plasma. Experimental measurements showed that the boundary layer thickness and the shock wave angle increased when the discharge was ignited. The current work was performed with two nozzles generating Mach 4 flows but at two different static pressures: 8 and 71 Pa. These nozzles were chosen to study independently the impact of the Mach number and the impact of the pressure on the flow behavior. In the range of the discharge current considered in this experimental work, it was observed that the shock wave angle increased with the discharge current of + 15 % for the Mach 2 flow but the increase rate doubled to + 28 % for the Mach 4 flow at the same static pressure, showing that the discharge effect is even more significant when boosting the flow speed. When studying the effect of the discharge on the Mach 4 flow at higher static pressure, it was observed that the topology of the plasma changed drastically and the increase in the shock wave angle with the discharge current of + 21 %. © 2017, Springer-Verlag Berlin Heidelberg.


Ren Y.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Grosselin B.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Daele V.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Mellouki A.,CNRS Institute for Aerothermal Combustion Reactivity and Environment
Faraday Discussions | Year: 2017

The rate constants for the ozonolysis of isoprene (ISO), methacrolein (MACR) and methyl vinyl ketone (MVK) have been measured using the newly built large volume atmospheric simulation chamber at CNRS-Orleans (France), HELIOS (Chambre de simulation atmosphérique à irradiation naturelle d'Orléans). The OH radical yields from the ozonolysis of isoprene, MACR and MVK have also been determined, as well as the gas phase stable products and their yields. The secondary organic aerosol yield for the ozonolysis of isoprene has been tentatively measured in the presence and absence of an OH radical scavenger. The measurements were performed under different experimental conditions with and without adding cyclohexane (cHX) as an OH radical scavenger. All experiments have been conducted at 760 torr of purified dry air (RH < 1%) and ambient temperature (T = 281-295 K). The data obtained are discussed and compared with those from the literature. The use of the HELIOS facility and its associated analytical equipment enables the derivation of kinetic parameters as well as mechanistic information under near realistic atmospheric conditions. © The Royal Society of Chemistry.


Tsikata S.,CNRS Institute for Aerothermal Combustion Reactivity and Environment | Heron A.,Ecole Polytechnique - Palaiseau | Honore C.,Paris-Sorbonne University
Physics of Plasmas | Year: 2017

In recent numerical, theoretical, and experimental papers, the short-scale electron cyclotron drift instability (ECDI) has been studied as a possible contributor to the anomalous electron current observed in Hall thrusters. In this work, features of the instability, in the presence of a zero-electron emission material at the thruster exit plane, are analyzed using coherent Thomson scattering. Limiting the electron emission at the exit plane alters the localization of the accelerating electric field and the expected drift velocity profile, which in turn modifies the amplitude and localization of the ECDI. The resulting changes to the standard thruster operation are expected to favor an increased contribution by the ECDI to electron current. Such an operation is associated with a degradation of thruster performance and stability. © 2017 Author(s).


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.


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.


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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