The Characteristics Of Atmospheric Pressure Plasma Jet Interacting With Liquids

Plasma is a state of matter consisting of cations and anions,in which low temperature plasma has been widely used in environmental remediation,material synthesis,biological engineering,clinical medicine.Particularly in the subject of clinical medicine,the atmospheric pressure plasma jet,capable of generating low temperature plasma in open space,has attracted great attention in sterilization,wound healing,cancer treatment.Usually,the surface of cellular tissue is covered by a thin blood serum-like liquid layer of a few hundred micrometers thickness.The thin liquid layer approximately contains 93%water and 7%proteins.Acting as a filter,the thin liquid layer modifies the concentration and the composition of the reactive species.The properties of the plasma have changed greatly because of the existence of the liquid layer.It is of great significance to study the characteristics of atmospheric pressure plasma jet interacting with liquids.In this thesis,firstly,the background of the model topology of atmospheric pressure plasma jet device is summarized.Secondly,using the numerical simulation to study the characteristics of atmospheric pressure plasma jet discharge process,as well as the interaction between the atmospheric pressure plasma jet and the solution.Last but not least,the atmospheric pressure plasma jet device is designed and developed.In the whole thesis,the basic principle,numerical calculation,mathematical derivation,parameter analysis,important results,are discussed in detail.The final results are as follows:1.In the chapter of the numerical simulation of helium-oxygen atmospheric pressure plasma jet,20 species and 49 reactions are selected.Based on the mass conservation,momentum conservation,energy conservation and the boundary conditions of electron emission,a two-dimensional fluid model with the needle-plane electrode construction is built up to numerical investigate the spatio-temporal evolution characteristics of the electric field intensity and electric potential.The results indicate that,the region of high electric field propagates to the plane electrode.The region of low electrode field occurs between the head of the ionization wave and the needle electrode along the propagating process.The region of high potential increases continuously in the direction of the ionization wave propagating.2.In order to regulate the concentration of active species in the helium-oxygen atmospheric pressure plasma jet.The main generating and consuming reaction pathway maps of oxygen species are studied.It shows that electron attachment reactions produce O^-and O₂^-.More than 80%of positive ions O₂⁺and H₂O⁺come from penning ionizations between He^*and molecules O₂ and H₂O.O and O?¹D?mainly dominated by e+O₂?e+O+O?¹D?.69.3%and39.2%of OH are produced by O?¹D?+H₂O?2OH and O+H+H₂O?OH+H₂O respectively.2O₂+O?O₃+O₂ is the key reaction for the formation of O₃.3.In the chapter of the numerical simulation of helium-oxygen atmospheric pressure plasma jet interacting with liquids,19 species and 39 reactions are selected.Based on the flux conservation,Henry's law,Poisson's equation,diffusion equation and diffusion-drift equation,a one-dimensional model is carried out to simulate the concentrations spatial distributions of different species.The simulation results demonstrate that H₂O₂ is a persistent molecular compound in the liquid phase region.O₃ and OH have relatively higher concentrations in the shallow region of water.The penetration depth of O₃,OH and HO₂ are approximately the same.4.In order to regulate the concentration of the mass transfer process from atmospheric pressure plasma jet to water,the main generating and consuming reaction pathway maps of high-concentration and low-concentration species are studied.H₂O₂ is mainly produced by O?¹D?+H₂O->H₂O₂ due to the continuous mass transfer of O?¹D?from atmospheric pressure plasma jet to water.In addition,2OH->H₂O₂ also generates a great deal of H₂O₂ in the liquid phase region.5.After comprehensively analyzed the development of atmospheric pressure plasma jet experiment,it is necessary to design a low-cost,low-temperature,low-power atmospheric pressure plasma jet device combining industry-university-research.The DBD-like topology is selected.The design of electrode,matching network and the optimization of atmospheric pressure plasma jet by pulse modulation are described in details.