Wyniki 1-3 spośród 3 dla zapytania: authorDesc:"Ben-Yssaad KRALOUA"

DC glow discharge modelling by using electrons transport parameters from the BOLSIG+ code DOI:10.15199/48.2019.01.50

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In a DC glow discharge, the electric field is homogeneous in the inter-electrode space. The ions striking the cathode create secondary electrons. The electron avalanche creates much electron that ions but electrons being 100 times faster than ions, they drift quickly to the anode where they are absorbed. The ions having a lot of inertia accumulate in the inter-electrodes space, then the number of ions accumulates increases and from an accumulation threshold, the electric field is no longer homogeneous while it decreases on the side anode, which has the effect of slowing the electrons that drift towards the anode. The process continues until the electric field at the anode vanishes. The electrons can no longer pass freely to the anode and are considerably slowed down. The electron number density increases until to equal of the density of ions. A plasma is formed near the anode. The number of charged particles increases and the plasma extends from the anode to the cathode. The extension of the plasma compresses the region of strong field towards the cathode. These phenomena continue until the creation of charged particles is equilibrate (creation=losses). Two regions appear, the sheath and the plasma. The majority of electric discharge in gases (plasma) are built upon the Boltzmann equation. In principle, the combination of the Boltzmann equation, together with the Maxwell equations, needed for computation of the electromagnetic field, describes the physics of many discharges completely provided that this set of equations is equipped with suitable boundary conditions. In practice, however, the Boltzmann equation is unwieldy and cannot easily be solved without making significant simplifications. Fluid models describe the various plasma species in terms of average hydrodynamic quantities such as density, momentum and energy density. These quantities are governed by the first three moments of the Boltzmann equation: continuity[...]

Two-dimensional modeling positive and negative streamer discharge at high pressure DOI:10.15199/48.2018.06.05

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The simulation of a streamer in electric discharge is not a new problem. Indeed, for many years authors have proposed first the simulations in one dimensional considering only the phenomena on the axis. These onedimensional models remain limited and do not fully account for the physics of discharge. This is why many authors have focused on two-dimensional modeling. The basics of the streamer theory were developed by Raether [1], Loeb and Meek [2]. In their model, we explain the movement of the discharge by that of an ionization front that propagates within space between two electrodes. Once the discharge is initialized, we notice that its propagation is assured without the help of any outside agent. Since the propagation of a streamer depends only on its own space charge field, it can propagate towards the cathode or towards the anode. This possibility makes it possible to define two types of streamers: negative streamer (also called Anode-Directed Streamers) and positive streamer (also called Cathode-Directed Streamers) [3]. We describe the results of numerical calculations of negative and positive streamer propagation based on a fully two-dimensional algorithm, which apply of fluxcorrected scheme names ADBQUICKEST to correct and follow the strong density gradients [4]. The development of this algorithm has allowed us to investigate problems in streamer propagation of considerable interest [5][19]. This work presents the results of the algorithm application to questions including the streamer propagation on ionization ahead of the streamer, on applied photoionization and ionization term, on applied field, on initial and boundary conditions for both case of streamer. 2. Model formulation 2.1 Studied configuration The computational domain is a cylinder of radius R = 0.5 cm (Figure 1) [6]. This domain is limited by two metallic electrodes parallel, planes and circular separated by a distance d equal to 0.5 cm. The applied[...]

Modeling glow discharge at atmospheric pressure in argon DOI:10.15199/48.2018.07.47

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Atmospheric Pressure Glow Discharge controlled by dielectric barriers (APGD) plasma sources driven by a radio frequency (RF) power supply are developed to obtain non-equilibrium gas discharge plasmas with large area, high stability, uniformity and reactivity [1,2]. Recently, atmospheric pressure discharges have found several industrial and other applications such as thin film deposition, surface modification, ozone generation, sterilization, bio-decontamination and others. In principle, atmospheric pressure plasma devices can provide a crucial advantage over low-pressure plasmas because they eliminate complications introduced by the need for vacuum [3]. The benefit of their use lies in the fact that they offer the possibility of low production cost without the need for vacuum equipment. The dielectric barrier discharge (DBD) is a common plasma source used for these applications [2]. Most of atmospheric pressure discharges are dielectric barrier discharges (DBDs) operating in the kilohertz [4]. New sources running at much higher frequencies in the RF range are currently under investigation [1, 2, and 3]. Model formulation In this work, the model used to describe the kinetics of the charged particles for the RF glow discharge at atmospheric pressure is the second order fluid model. It is based on the first three momentums resolution of the Boltzmann equation. These three moments are continuity, momentum transfer and energy equations, which are strongly coupled with the Poisson’s equation by considering the local electric field approximation for ions and the local mean energy approximation for electrons. In the present model, the transport equations derived from the first three moments of Boltzmann's equation are written only for electrons and positive ions (1) e e e n Φ S t x       (2) n Φ S t x      [...]

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