| Atmospheric pressure plasma jet, which has caused great concern in internationalcommunity, is a new type of gas discharge technology developed in recent years, andhas become important research topic in the field of gas discharge. Compared to theconventional type of DBD (Dielectric Barrier Discharge, DBD), atmospheric pressureplasma jet ejects the plasma out of the discharge chamber and directly into the openingatmosphere by strong airflow. The plasma region and high voltage electrode areseparated from each other which lead a higher safety for operators. At the same time, itis rich in active substances and the temperature of plasma can be as low as roomtemperature, which highlights a great prospect in the surface modification of materials,plasma chemistry, biomedical and other fields. Currently, lots of research at home andabroad focuses on physical mechanism of the plasma jet source and its developmentprocess, discharge characteristics, jet applications etc., but few scholars consider theelectrode structural optimization and the discharge characteristics for this kind of studyare not thoroughly. Moreover, the simulation study about the jet is rarely reported.In response to the issues above, this study mainly focuses on DBD-typed plasmajets, and a more comprehensive study of influencing factors on jet characteristics is tobe carried out through sterilization experimental. At the same time, the air plasma jetdevices based on MHCD (Micro-hollow cathode discharge, MHCD) is designed andsome electrical characteristics will be tested. Therefore, the main contents can besummarized as follows:First of all, the basic conception, application prospect and significance of the studyare briefly introduced. Current researches about the plasma jets based on DBD andMHCD are deeply reviewed, simultaneously.Secondly, the basic theory of gas discharge and several typical discharge formsare introduced. The two-dimensional electric/flow field coupling model are built byusing Comsol/Multiphysics software for the involved types of jet structure, that is theouter ring electrode (single electrode and double-wrapped electrode) and needle-ringelectrode configuration. The distribution of electric and flow field characteristics can beobtained through the simulation and all the simulation results are benefit to thesubsequent experimental studies.Thirdly, the experimental system is build for atmospheric pressure helium plasma jet. More impact factors, that is electrode position, electrode parameter, external air flowas well as the applied voltage, are studied combined with basic theory of electric andflow field, and the physical mechanism of experiment phenomena is offered. Themulti-pulse discharge appears on double-wrapped electrode during the experiment. Theinfluencing factors of dissipated power for jet in helium and helium/air are discussed,simultaneously. The helium/air plasma jet is used for the sterilization of E.coli andresults prove the correctness and feasibility of proposed method.Fourthly, the asymmetry multi-pulse discharge is observed on designed needle-ringelectrode configuration during experiment. Meanwhile, it is found that the number ofcurrent pulse is deeply influenced by electrode parameter, and the relevant physicalmechanism is given. In addition, the influencing factors for jet length as well asdissipated power are explored under pure helium and helium/air mixture. Thesterilization experiment is developed for E. coli, accordingly.Finally, the air plasma discharge device based on MHCD is designed and the stabledischarge under opening atmosphere is realized. The related electrical characteristics arestudied, and parts of the experimental results are acquired which laid the foundation forthe realization of air plasma jet. |
PDF Full Text Request