Study On Spatio-Temporal Evolution Of Liquid-phase DC Cathode Glow Discharge

The generation of low-temperature plasma has little demanding on environmental conditions,power supply and the reactor is put in to less equipment.It is suitable for convenient and flexible hydroge n production in small and medium scale,especially in the case of glow discharge plasma in liquid state.During the reaction process,a product which does not appear in ordinary electrolysis is obtained,and when it is used for hydrogen production,the hydrogen produc tion efficiency can be improved,and the electric energy consumptio n can be reduced.In high-temperature plasmas,high-activity particle s with high energy density can increase the rate of hydrogen produ ction and initiate new chemical reactions.Because of the raw mater ials for hydrogen production by plasma method,such as methane a nd ethanol,are liquids,the generation of discharge plasma in a liqu id state is a key technology to be solved at present.This thesis is concerned with the theoretical and experimental research on the spat iotemporal evolution of liquid-phase DC cathode glow discharge.First,a theoretical analysis model for liquid-phase DC cathode glow discharge evolution including avalanche establishment,avalanch e,and discharge is established.Analyze the variation of electric fiel d strength,cathode emission current density,reaction ambient tempe rature and reaction solution in the space-time evolution of discharge by Matlab software and use the Comsol Multiphysics multiphysics simulation software to simulate the relationship between preset bub bles near the liquid cathode and electric field strength and current density.Simulation results show that the starting condition of liquid phase glow discharge is the emission current density at the cathod e tip,also show that the electric field inside the bubble is greatly enhanced because of the superposition of the applied electric field and the polarization electric field,making the substance in the bubbl e ionization faster than the liquid and by increasing the applied vol tage can effectively accelerate the breakdown process of the bubble.Then,design a liquid-phase DC cathode glow discharge experi mental device and experimental scheme,develop an H-type reactor,select the reaction materials and dimensions and determine the expe rimental diagnosis method of space-time evolution of liquid-phase D C cathode glow discharge plasma by combining electrical method a nd optical method.Then,according to these designs,build a liquid-phase DC cath ode glow discharge experimental device to carry out experimental r esearch on the spatiotemporal evolution of liquid-phase DC glow di scharge.The experiment uses ethanol solution as the medium,use h igh-speed capturing time-resolved image of transient liquid-phase D C cathode glow plasma discharge.The image processing is perform ed by NI-IMAQ Vision,and the curve of current characteristic is c ombined to analyze the evolution of the space-time evolution of the discharge.The experimental results show that the bubble is increas ing and deforming most of the time before the discharge breakdow n.The continuous action of the electric field promotes the generatio n of low-density regions and enhances the ionization process of the liquid phase,resulting in multiple intermittent glow discharge phen omena.Finally,carry out an experimental study on the influencing fact ors of liquid-phase DC cathode glow discharge.The experimental st udy found that when the applied voltage is between 100~600V,In a solution of 99.7% ethanol in a solution temperature of 70°C,The best conductivity of the solution is 3.2mS·cm-1.which the glow dis charge area is large,and the breakdown voltage can be lowered.The cathode immersion length of 4 mm is the best,at this time,the d ischarge can be successfully started at the near boiling point,and t he consumables are saved.All the research results show that adjusting the applied voltage strength is a way to effectively influence the shape distortion and excitation ability of the bubble.The breakdown voltage of the bubb le is inversely proportional to the conductivity of the solution.The depth of the cathode immersion solution is inversely proportional to the breakdown voltage.