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Home > Seminars and Workshops > Past seminars, PhD & HDR defense > 2016 > Soutenances de thèses et HDR 2016 > Le vendredi 16 décembre à 10h

Le vendredi 16 décembre à 10h

Sergey Shcherbanev’s PhD defense

When: 16th of December 2016 at 10:00am

Where: Ecole Polytechnique, amphi Becquerel

Title: Filamentary nanosecond surface dielectric barrier discharge at elevated pressures. Streamer-to-filamentary transition and application for plasma assisted combustion

Abstract:
Non-equilibrium plasma is one of the most attractive and promising tool for many plasma-assisted applications. Production of active species (excited species, radicals, high energetic photons covering UV and IR spectral range) is important for gas pollution control, surface treatment, plasma actuators for aerodynamics application, biomedical applications and more recently the field of plasma medicine. For atmospheric and elevated gas densities the mainstream of the non-thermal plasma applications is the ignition of combustible mixtures or so-called Plasma-Assisted Ignition (PAI).
Surface dielectric barrier discharges (SDBDs), widely used for aerodynamic flow
control, were recently suggested as distributed initiators of combustion in different systems. A principal possibility of using the SDBD igniters at as high pressure as tens of bars has been demonstrated during the last 4-5 years. At the moment of the beginning of the thesis, the set of experimental data on the discharge and of ignition of fuels with SDBD was insufficient for detailed analysis. Therefore, the experimental study of the surface DBD at atmospheric and elevated gas densities and the study of flame initiation with nanosecond SDBD were the object of the presented thesis.
The results in the Thesis are presented in three parts. In the first part the nSDBD in a single shot regime at atmospheric air is investigated. The analysis of energy deposition, discharge current, intensity distribution and consequent energy release is performed. The positive and negative polarity pulses are used to produce surface discharge. The physics of anode and cathode-directed streamers is discussed. For both polarities of the applied pulses the electron density and reduced electric field are estimated and compared with calculations and/or 2D modeling results. The second part is devoted to the study of nSDBD at elevated pressures, up to 12 bar, in different gas mixtures (N2, air, N2:CH4, N2:H2, Ar:O2, etc.). Two morphologically different forms of the nSDBD are considered: a "classical" streamer DBD at relatively low pressures and voltages, and a filamentary DBD at high pressures and/or voltages. The emission spectroscopy is used to obtain quantitative data about the discharge at high pressures (1–12 bar). The possible nature of the discharge filamentation is described.
Finally, the third part describes the experiments of plasma-assisted ignition with nanosecond SDBD at elevated pressures. The discharge morphology in lean combustible (H2:air) mixtures and following ignition of the mixtures are studied. The comparison of ignition by filamentary and streamer discharge at the pressures 1–6 bar is performed. Kinetic modeling of plasma assisted ignition for the electric fields typical for nSDBD, E/N = 100 − 200 Td is used for analysis of experimental data. Complex study of the discharges at atmospheric pressure, discharge at high pressures and ignition allow detailed description of the high-pressure, distributed in space ignition by non–equilibrium plasma.


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Tutelles : CNRS Ecole Polytechnique Sorbonne Université Université Paris Sud Observatoire de Paris Convention : CEA
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