Modélisation 2D et 3D d'un écoulement gazeux instationnaire activé par décharges couronne dans un réacteur multi-pointes plan dédié à la décontamination des gaz

Abstract : This thesis is dedicated to plasma reactors modeling and simulation using corona discharges for gases decontamination. These reactors are able to treat pollutants when they are present in very low concentrations (a few hundred ppm) in a gas mixture. However, each treatment requires specific studies of the reactor generally considered as a "black-box" which means that its efficiency is evaluated through global energy cost and input-output conversion rate. Indeed, the complex phenomena responsible of the pollutants transformation are spatially localized and strongly unsteady. They are therefore quasi inaccessible to experimental measurement. Thus, the goal of this thesis is to develop an efficient model able to follow and explain the reactive, energetic and hydrodynamic processes occurring in the filamentary discharges and which progressively extend to the entire reactor volume. This type of modeling will be useful in designing future reactors and also in minimizing the development costs. The thesis is divided into five main chapters in addition to the general introduction and the conclusion. The first chapter describes the main features of corona discharges like streamers at atmospheric pressure and all the energetic, hydrodynamics and kinetics phenomena that are generated by their passage. The second chapter presents the discharge and the reactive flow model equations. The latter is modeled by reactive fluid mixture equations coupled with the energy conservation equation of vibrational excited states. A state of the art of the corona reactor modeling is presented followed by a description of the FLUENT software, which has been chosen in order to solve equations of our model. Chapter 3 is dedicated to validate the model and the discharge-gas coupling in a 2D geometry. The simulation conditions are those of an experimental configuration of a mono-tip to plane reactor developed in the group and working with synthetic air under ambient conditions of temperature and pressure. The source terms injected during each periodic passage of the discharges are estimated from a validated simulation of the primary and secondary streamers development. The flow simulation involves 10 chemical species (including nitrogen and oxygen metastable states) reacting following 23 reactions. The obtained results allowed to validate the source terms injection and to follow in detail the gas temperature and chemical species evolutions in function of the flow type (laminar or turbulent), its orientation and the number of discharge crossing the gas. Chapter 4 concerns the 2D simulation of a multi-tip to plane reactor (up to 10 tips) until 10ms with a discharge repetition frequency equal to 10 kHz. The simulations allow to explain and follow in detail the ozone formation and the transformation of a chosen pollutant (nitrogen oxide NO) in function of the number of tips and the flow properties. The final chapter shows the first results obtained for a 3D geometry in the case of mono and multi-tip to plane.
Document type :
Theses
Plasmas. Université Paul Sabatier - Toulouse III, 2011. French


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Submitted on : Thursday, December 15, 2011 - 5:02:32 PM
Last modification on : Friday, December 16, 2011 - 9:12:42 AM

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Mohamed Meziane. Modélisation 2D et 3D d'un écoulement gazeux instationnaire activé par décharges couronne dans un réacteur multi-pointes plan dédié à la décontamination des gaz. Plasmas. Université Paul Sabatier - Toulouse III, 2011. French. <tel-00652493>

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