Study On The Characteristics And Mechanisms Of DC Glow Discharge Under External Gas Flow Disturbance At Atmospheric Pressure

Atmospheric-pressure cold plasma is receiving more and more attention due to many applications,such as thin film deposition,surface modification,biomedical engineering,generation of ozone,and pollution abatement.This is mainly resulted from its low-temperature and non-equilibrium characteristics,as well as the avoidance of vacuum equipment.Direct-current(DC)glow discharge is a popular method to produce non-equilibrium plasma.In practical applications,it has been found that external disturbance,such as gas flow and magnetic field,is beneficial to the production of cold plasma under certain conditions.In this way can we improve the performance of plasma sources,e.g.enhancing the plasma chemical activity and enlarging the plasma volume.In this work,the properties of DC glow discharge in the longitudinal flowing argon or helium at atmospheric pressure are investigated by employing a one-dimensional self-consistent fluid model.Firstly,the one-dimensional self-consistent fluid model was employed to investigate the influence of longitudinal argon flow on the DC glow discharge at atmospheric pressure.It is found that the charges exhibit distinct dynamic behaviors at different argon flow velocities,accompanied by a considerable change in the discharge structure.The positive argon flow allows for the reduction of charge densities in the positive column and negative glow regions,and even leads to the disappearance of negative glow.The negative argon flow gives rise to the enhancement of charge densities in the positive column and negative glow regions.These observations are attributed to the fact that the gas flow convection influences the transport of charges through different manners by comparing the argon flow velocity with the ion drift velocity.Secondly,the one-dimensional self-consistent fluid model was employed to characterize the DC glow discharge in longitudinal flowing helium at atmospheric pressure.Distinct dynamic behaviors of charges are observed at different helium flow velocities,accompanied by a great change of discharge structure.The positive helium flow leads to the reduction of charge densities in the positive column and negative glow regions.The negative helium flow allows for the gain of charge densities in the negative glow regions.These observations are attributed to the fact that the convection due to the gas flow influences the transport of charges throughdifferent manners by comparing the helium flow velocity with the ion drift one.The increase of charge density means the enhancement of plasma chemical activity.These findings are important for improving the chemical activity and work efficiency of plasma source by controlling the gas flow in practical applications.