Characteristics And Application Of Atmospheric Pressure Microwave Plasma Torch

Atmospheric pressure plasma is a kind of plasma with high chemical activity.Because it does not need low pressure environment and vacuum system,it has the advantage of high efficiency and high benefit,it has a wide potential application prospect in the fields of compound decomposition.In practical applications,discharge plasmas are often faced with complex working conditions,and atmospheric pressure microwave discharge as a plasma production mode closely combined with flow field and electric field,the flow field becomes the key factor that affects the efficiency of physical and chemical reactions in plasma.Therefore,it is necessary to study the microwave plasma with the focus on the flow field.In this thesis,the characteristics of Ar gas plasma torch under different working conditions are studied by using the selfdesigned atmospheric pressure microwave plasma experimental platform and the simulation results of plasma and flow field with COMSOL simulation software,and the discharge mechanism and phenomena of Ar gas plasma torch under different conditions are discussed with the combination of discharge morphology,spectrum theory and Ludwig Boltzmann slope method.The conclusions are as follows:The microwave plasma discharge of pure Ar gas at atmospheric pressure was studied.When pure Ar is discharged,the plasma length is mainly related to the low energy electron density excited by the second collision,the main reason for the length change is the entrainment of low energy electrons by gas flow,and the electron temperature increases linearly with the increase of gas flow rate.In contrast,in an open atmosphere,a large amount of Inelastic collision between the air particles and the excited state Ar in the discharge tube decreases the plasma length significantly,but the electron temperature increases.The results show that the increase of air flow leads to a large number of particles in the discharge tube and a significant increase in the macroscopic temperature of the gas.At the same time,with the introduction of complex particles,the plasma changes from filamentous discharge to tubular discharge,and Ar emission spectrum only has two obvious lines:Ar(588.85 nm)and Ar(671.92 nm).This indicates that there is a mechanism that the injection of air in the discharge process can guide the transition energy levels excited by Ar atoms to some extent.In the experiment,the influence of the flow field on the plasma morphology is realized by changing the distribution of different gases and the collision frequency of different kinds of particles.On this basis,experiments of Ar plasma injected with methane,carbon dioxide and other gases were carried out,and the changes of plasma characteristics were studied,the experimental results show that the orientation of different gases to the plasma is related to the ionization energy of the gas itself.The lower the ionization energy of the gas,the higher the Ar atomic excitation energy,the results are expected to provide experimental support for volatile organic compound(VOC)degradation and carbon neutral(CCUS)applications.