Fluid model of dielectric barrier gas discharge.

摘要

A two-fluid model of dielectric barrier gas discharge is presented in this thesis. The model predicts the physical structure of the gas discharge obtained between two electrodes, when one is covered with a dielectric material: It predicts the distribution of the electron and ion particle densities, electron energy, and electric field strength. It is a self-consistent numerical model, in which the dielectric properties of the dielectric material are included and the geometry of the electrodes is taken into account, thus coupling the charged-particle transport to the electric field.; New boundary conditions are developed for the electron gas at the anode; the results indicate that the common boundary conditions frequently used in the literature give solutions with non-physical behavior. The new boundary conditions give solutions with the expected physical behavior.; The equations of the model are formulated numerically using a Galerkin finite element method and solved using the Newton iteration method. New universal matrices for the finite element method are presented which can be used to construct complex finite element matrices, by replacing integrals with matrix products, in a consistent and uniform manner independent of element shape, dimensionality, and order.; Solutions for DC, pulse-waveform and time-harmonic applied electrode voltages for geometries with and without a dielectric barrier are presented. The regulating effect of the dielectric barrier by surface charge accumulation is shown for discharge under constant applied voltage, assuming a static temperature for the electron gas, for the full self-consistent model. Also, simulations of dielectric barrier discharge with applied pulse-waveform voltages are compared with simulations of applied time-harmonic voltages. The results show very similar period-averaged electric fields, electron temperature profiles, charged particle densities, and total conduction current densities. However, a much higher period-integrated ionization rate is obtained from voltage pulse simulations, compared to time-harmonic voltage simulations. Therefore, we obtain a greater reaction rate for an equivalent conduction current, in a period-averaged sense, for a discharge driven by pulse-waveform applied voltages than with time-harmonic applied voltages. Such a difference was not observed for simulations without the dielectric barrier.