Simulation Studies On Gas Temperature Characteristics Of An Atmospheric-pressure Dielectric Barrier Discharge

An atmospheric-pressure dielectric barrier discharge（DBD）has received widespread attention in scholars because of its simple structure and convenient operation.Many studies on atmospheric-pressure DBD mode have been carried out recently.The reported research works revealed the influences of the electrode voltage,the power supply frequency and the dielectric material on DBD mode.However,the influences of the gas temperature on DBD transition are scarcely reported.The gas temperature rising is high due to the frequent collisions of the heavy particles in an atmospheric pressure DBD,which will cause the contraction of discharge channel.Therefore,it is of great significance to study the gas temperature characteristics of atmospheric-pressure DBD for the stability and controlling of gas discharge plasma.In this paper,an atmospheric pressure DBD model is established by COMSOL multi-field coupling simulation software.Atmospheric pressure DBD mode transitions from columnar to uniform discharge and surface to volume discharge are studied in detail.The role of radial reduced electric field(E_rr)is discussed.The main research works are as follows:（1）The evolution of an atmospheric-pressure DBD column along with E_rr and surface charge density with gas temperature is studied by numerical method.We firstly calculate the spatial distributions of some physical parameters such as electron number density,helium atomic number density,ionization rate.Voltage and current waveform and breakdown voltage at different gas temperatures are obtained.It was found that a helium discharge can evolve from discharge columns to homogeneous discharge,and the breakdown time advances and the gas breakdown voltage decreases with the increase of gas temperature.Then the gas temperature characteristics of spatial distribution of E_rr and surface charge density are obtained.The gas temperature characteristics of the spatial distribution of E_rr is used to explain the evolution of column discharge.（2）An atmospheric-pressure DBD is studied at temperatures ranging from room temperature down to 200.0 K.Firstly,the spatial distribution of various particles（electron,nitrogen molecule and nitrogen molecule ion）,breakdown voltage and discharge current under different gas temperature were obtained.The simulation results show that with the decrease of gas temperature,the discharge gradually transits from surface to volume discharge;the column discharge moves to the radial center of the electrode,and the breakdown voltage gradually increases.The relations between surface discharge and Townsend discharge,volume discharge and glow discharge are discussed.Then the variation of electron density with time is explored.Finally,the distribution of E_rr is also calculated and analyzed under different gas temperature.It was found that the direction of the E_rr of the dielectric surface near the discharge center is different when discharge mode is different.Specifically,the E_rr on both sides of the discharge center pointed to the discharge center when the discharge is surface discharge,and is the opposite direction when the discharge is volume discharge.With the decrease of gas temperature.