Simulation Of Repeated Frequency Discharge Plasma Characteristics In Aqueous Solution

Plasmas are known to be the fourth state of matter.In recent years,progress on the application of plasma has been made in various fields,especially in medicine,environment and other aspects.However,at present,there are many studies on atmospheric pressure cold plasma,while studies on plasmas in water are rare.In recent years'studies,it is found that the active substances produced in the discharge process in water are not only large in quantity but also various in variety.At the same time,the active substances are also accompanied by the generation of shock wave,ultraviolet light and other phenomena.Active substances greatly enhance the ability of plasma sterilization and pollutants degradation.Moreover,compared with the traditional sewage treatment,the water pulse discharge technology do not need to add other chemical substances and has no secondary pollution,which has attracted wide attention.Therefore,the research of the water pulse discharge has become an important subject at present.In this paper,the pulse discharge process in water is studied from two aspects:experiment and simulation.In experimental aspect,the the mechanism of streamer discharge and the physical process of bubble initiation,propagation and dissipation are studied.With double pulse breakdown time after discharge air bubbles in the development process of experiments to explore the effect of the dielectric recovery characteristics of water,at the same time use the stark broadening spectral measuring underwater pulse discharge plasma temperature and electron density,according to the experimental results,pulse discharge plasma in the average temperature is about 15000 K,peak electron density is about 10¹⁸ cm^-3orders of magnitude.In the aspect of simulation,the theory of water pulse discharge is still not perfect and needs further research.In order to optimize and realize the underwater pulse discharge water treatment system,modeling is one of the essential works.Based on two-dimensional axisymmetric model,the formation and extinction mechanism of active substances are studied by simulation.In the simulation of this topic,the water vapor as the background gas,the discharge process in a period is simulated,including electron density,electron temperature,electric field distribution and the main active particle space and time distribution.More than ten kinds of electron collision reactions and more than 30 kinds of complex chemical reactions are selected in the model,and the calculation amount is reduced on the premise that the simulation results are accurate.The effects of applied conditions on the generated electrons and active particles,including voltage peak and bubble diameter,are studied.The results show that with the increase of voltage peak or the decrease of bubble radius,the electron density and energy peak of plasma increase,and the number of active particles also increases to different degrees.Therefore,the generation efficiency of active particles can be improved by appropriately increasing the input voltage peak and reducing the gap distance in the gas region.