Research On Plasma Characteristics Of Parallel Magnetic Field Enhanced Nanosecond Pulse DBD

Nanosecond pulsed dielectric barrier discharge plasma has attracted wide attention in the field of non-thermal plasma research and applications due to its advantages of lower discharge plasma temperature,lower energy consumption,and higher active particle concentration compared to AC power supply excitation.In order to improve the application performance of dielectric barrier discharge plasma,it is urgent to obtain a nanosecond pulsed dielectric barrier discharge with stronger intensity,as well as higher active particle density.Previous studies have found that the high-energy electrons were subjected to the Lorentz force to perform the Lamor vortex motion under the action of magnetic field,which can increase the motion path of highenergy electrons in gap,increase the frequency of electron collision and the degree of ionization.Therefore,the discharge current can be enhanced,the discharge area can be increased,and the density of active particles can be increased.However,less attention has been paid to the characteristics of magnetic field enhanced nanosecond pulsed dielectric barrier discharge,and the influence of pulse voltage parameters and dielectric condition on the magnetic field enhanced discharge are still unclear.In this paper,a permanent magnetic field is used to provide a constant magnetic field parallel to the direction of the electric field.The effect of magnetic field on the nanosecond pulse needle-plate dielectric barrier discharge characteristics is studied.Firstly,the effect and mechanism of parallel magnetic field on needle-plate dielectric barrier discharge were studied,and the feasibility of using magnetic field to enhance the discharge was proved.Secondly,based on the above research,the effects of dielectric materials and pulse parameters on the magnetic field enhanced needle-plate dielectric barrier discharge intensity are investigated.The effects of dielectric materials and thickness on discharge conduct current,energy and image,and the effects of different pulse voltage parameters on the characteristics of needle-plate dielectric barrier discharge are specifically analyzed.The electrical and optical characteristic of discharge with and without magnetic field are analyzed and explained.The main experimental results are as follows:1)The effects of magnetic field on the needle-plate dielectric barrier discharge under different dielectric conditions were investigated.It was found that the dielectric with larger dielectric constant discharges more strongly,and the size of surface discharge area is closely related to the magnetic field enhancement effect.The DBD discharge intensity with ceramic dielectric is stronger than that of quartz,but the surface discharge ductility with quartz is better and the area is larger.Thence,the enhancement effect of the magnetic field is more obvious with the quartz as the dielectric than that with the as the ceramic.2)The effects of pulse amplitude,rise time and fall time on the electrical and optical characteristics of the magnetic field enhanced needle-plate dielectric barrier discharge were studied separately.The magnetic field has a significant enhancement effect on the conduct current,power,energy,and light intensity under different pulse parameters.The effect of the magnetic field increases the ionization degree of the discharge reactor and enhances the discharge.At the same time,the accumulation of positive charges on the surface of the dielectric increases,which leads to the establishment of the reverse electric field in advance and the increase of the reverse current.In addition,the effect of the magnetic field on the discharge is different under different pulse conditions.(1)When the pulse amplitude increases,both the discharge current and the photocurrent increase,the number of active particle species increase,and the central cylindrical area of the discharge image is more obvious.(2)When the pulse rise time increases from 50 ns to 250 ns,the electric field change rate decreases,the discharge intensity weakens,and the plasma discharge area increases.Moreover,the accumulation time of positive charge on the surface of dielectric increases,resulting in a gradual increase of negative current.When the rise time is 100 ns and 150 ns,the increase of the space discharge area leads to the increase of the vertical magnetic field velocity of high-energy electrons.Since the discharge intensity of ceramics is greater than that of quartz,and more charged particles are ionized,the effect of the magnetic field on the ceramics as a dielectric is greater than that of quartz at this time under this condition.(3)The pulse fall time has little effect on the discharge result,but the discharge energy and light intensity can be adjusted by changing the pulse fall time in small steps.3)The ozone output of dielectric barrier discharge was measured with and without magnetic field under different pulse voltage parameters.It was found that the magnetic field effect significantly increased the ozone output,and the ozone output was mainly related to the number and intensity of filamentary discharges.As the frequency of the pulse voltage increases,the enhancement effect of the magnetic field on the discharge ozone output gradually increases;when the pulse voltage amplitude increases from 12 kV to 14 kV,the ozone concentration increases from 9.88 ppm to 25.07 ppm when the magnetic field is applied,which is about 1.78 ~ 2.48 times that without the magnetic field;when the rise time is 250 ns,the magnetic field has the most significant effect on the ozone output of the needle-plate dielectric barrier discharge,which increases the output of ozone from 5.56 ppm to 16.78 ppm;when the fall time increases,the discharge ozone output gradually decreases under the action of the magnetic field,and the ozone output under the action of the magnetic field is approximately 2.20 ~ 2.71 times that without the magnetic field.