Generation And Application Of Air Glow Plasma Jet

In recent years,the low-temperature plasma generated by the atmospheric pressure plasma jet has shown extremely broad application prospects in many aspects.However,most plasma jets are generated under inert gas or gas flow conditions.The formation and development mechanism of atmospheric pressure air glow low-temperature plasma jets were rarely studied.In this paper,through the combination of theoretical analysis and experimental research,the electric field simulation and experimental measurement,study the necessary conditions for forming glow plasma jet under atmospheric pressure air,needle-plate electrode discharge with large current-limiting resistance and the influence of the dielectric tube on the movement of charged particles.Developed two plasma jet generators based on atmospheric pressure air,and conduct experiments on the freshkeeping with plasma.Firstly,based on the formula derivation of the mean free path of electrons and plasma density in atmospheric pressure air,it is concluded that the difficulty of forming glow discharge in atmospheric pressure air lies in high electric field intensity and high plasma density,which makes glow discharge easy to transform into filamentous or arc discharge.Based on the development theory of electron avalanche,two control methods are proposed to realize the air glow discharge,that is,to provide enough initial electrons for the discharge and to reduce the electric field intensity in the discharge space on the basis of maintaining the discharge.Finally,analyze the realization methods of the two control methods.Secondly,the generation characteristics of pin plate electrode discharge based on large current limiting resistor are studied in atmospheric pressure air environment,and the differences of discharge development process under different polarity are discussed.The resistor can act as a voltage divider,resulting in the decrease of electric field intensity and the increase of initial electrons.It also limits the excessive development of current,which can effectively inhibit the conversion of discharge.The development process of positive discharge is from anode to cathode.The negative polarity is the result of the interaction between anode and cathode.The existence of anode dark area is the effect of positive ion net space charge layer.The discharge channel has a certain voltage due to the existence of dark area.Then,the influence of dielectric tube on the discharge process is analyzed.The radial and lateral electric fields at the head of the discharge channel are restrained by the accumulation of charges on the wall of the dielectric tube.The resistance of the discharge channel increases,the initial voltage of the discharge increases and the discharge current decreases.The dispersion of the discharge is better,and it is more inclined to soft glow discharge.The dielectric tube reduces the space electric field in front of the tip,which makes the negative discharge develop from the nozzle first.After the discharge channel is turned on,in addition to the anode dark area,multiple dark areas will be formed with the increase of voltage,due to the formation of virtual electrode in the net space charge layer at the tip and nozzle.The existence of dielectric tube also increases the discharge temperature,and the discharge temperature of negative electrode is significantly higher than that of positive electrode.Finally,based on the above discharge theory and experiment,a handheld plasma jet generator is made,which can generate 5mm low temperature plasma jet in atmospheric air.The effect of plasma fresh-keeping under different treatment time is tested by the device.The result shows that the plasma can effectively maintain the moisture content of fruits and vegetables,reduce the enzymatic browning rate and increase the storage time.Finally,a plasma jet array is designed and assembled based on STM32 platform,which can follow the height of the object surface.