Numerical Study Of Atmospheric Pressure Pulse-modulated Radio-frequency Dielectric Barrier Discharge In Argon-oxygen Mixture

In recent years,atmospheric low-temperature plasma has been widely used in fields such as assisted combustion,microbial mutation breeding,treatment of harmful substances,and surface modification of materials,and has also spawned emerging disciplines such as plasma medicine.As atmospheric pressure low-temperature plasmas are increasingly used in biomedical applications,researchers have discovered that reactive oxygen species?ROS?of plasma play a key role in the promotion of human health in applications such as medical device sterilization,wound healing,and accelerating cancer cells'death.The atmospheric pressure radio-frequency glow discharge in the mixed oxygen is the main way to produce ROS,however,due to its high power frequency,the discharge is prone to instability and easily transferred from glow to arc.Studies have found that if a pulse modulation is applied to a discharge power supply,the transition of the discharge mode can be controlled by adjusting the pulse parameters,thereby realizing a high-intensity and stable glow discharge.In this paper,pulsed modulation is applied to the radio frequency Ar-O₂ mixed dielectric barrier discharge power supply under atmospheric pressure.By establishing a fluid model and using the SG algorithm,the pulse stabilization phase of glow discharge is studied.1.Assuming the oxygen concentration is constant,the discharge characteristics of the mixed gas of argon and oxygen were studied.The research contents mainly include:gas discharge voltage,current density,electron density,average density of argon and oxygen species,and spatial distribution of electron temperature and electric field.The discharge voltage and current density waveforms are basically maintained in a sinusoidal shape,and the discharge is an atmospheric pressure radio-frequency glow discharge.2.The effects of oxygen concentration on the discharge characteristics have been studied.With the oxygen concentration increasing,the interaction between electrons and oxygen molecules is more frequent.Due to the adsorption of oxygen,the electron density in the space decreases,the chemical reactions related to electrons become weak,and the current density,electron temperature and electric field decrease.However,under different oxygen concentrations,the changing rules of ROS are different.In this paper,the evolution law of the density of each ROS with oxygen concentration is analyzed in detail.3.Under the condition of other discharge conditions unchanged,the influence of discharge gap on basic discharge characteristics and ROS was discussed.As the discharge gap increases,the maximum discharge current density and the discharge intensity decreases.In the sheath region,the electron temperature and electric field decrease as the discharge gap increases,and the sheath becomes thinner.4.The effects of pulse parameters on the characteristics of Ar-O₂ mixed discharges are discussed in detail.Firstly,the effects of modulation frequency and duty cycle are discussed.Studies have shown that reducing the modulation frequency or increasing the duty cycle will increase the number of RF cycles,resulting in increased power density,increased power density coupled into the plasma,and enhanced discharge.Secondly,when the amount of oxygen added is different,the variation of the density of ROS at different modulation frequencies is discussed.For different oxygen contents,the modulation frequency has a great influence on the oxygen atom and oxygen molecular density.The effect on the excited oxygen atoms gradually decreases with increasing oxygen content.When the oxygen content is low,the modulation frequency has little effect on the ozone density.With the increase of oxygen content,its influence gradually increases.