Study On The Uniformity In Helium Dielectric Barrier Discharges At Atmospheric Pressure Driven By Sinusoidal And Narrow Pulse Voltage

Dielectric barrier discharge(DBD)at atmospheric pressure is a common method to generate cold plasma.Within a certain range of parameters,the discharge is stable and uniform,which has a good industrial application prospect.However,the discharge appearance of atmospheric pressure DBD is very sensitive to the change of applied parameters,and it is prone to uneven discharge,which is not conducive to the application in industrial fields with high requirements of discharge uniformity.At present,people have limited understanding of the transformation and operation mechanism of discharge uniformity.To further understand the transformation and evolution mechanism of discharge uniformity,this paper adopts the fluid models and experiments to study the discharge uniformity driven by sinusoidal and narrow pulse power supply.The main contents include:(1)When the discharge is driven by sinusoidal voltage,the influence of increasing gap width(d_g)on radial uniformity in atmospheric helium DBD with parallel plates is studied by using two-dimensional axisymmetric fluid models.By analyzing the changes of physical quantities such as electron density,ion density,electric field,surface charge and radial electric field,the influence of d_gon the transformation and evolution trend of discharge uniformity are studied and the physical mechanisms are explored.(2)When the discharge is driven by narrow pulse voltage,one-dimensional fluid models are used to study the phenomenon and mechanism of electron density stratification in axial space caused by multiple-current-pulse mode in atmospheric helium DBD with parallel plates;Two-dimensional axisymmetric fluid models are used to study the influence and evolution mechanism of quasi-uniform discharge on radial space with the change of applied voltage amplitude(V_am);The discharge experiments driven by narrow pulse voltage are carried out to study the multiple-current-pulse phenomenon and the influence of V_amaltering on radial discharge characteristics.Through the above researches,this paper obtains some understandings in atmospheric helium DBD with parallel plates,including:driven by sinusoidal power supply,with the increase of d_g,the discharge evolves from quasi-uniform discharge to columnar discharge,and finally evolves into quasi-uniform discharge;The factors of discharge uniformity transformation and evolution mainly include electron cascade,surface charge,electron backflow and radial electric field;When the discharge is driven by narrow pulse power supply,the multiple-current-pulse phenomenon causes the electron density stratification in axial space,which is closely related to the increasing electric field in the cathode fall region,and when V_amincreases,the radial discharge area increases under quasi-uniform discharge,which is related to the enhancement and distortion of the spatial electric field in the radial edge region.