Study On Key Issues Of Constructing Large-scale DBD Oxygen Plasma Source

In recent years, oxygen plasma technology has shown promising application prospects in materials surface modification, laser generation, semiconductor manufacturing, ozone generation and environmental fields, in particular, the oxygen plasma technology has been successfully employed to ship ballast water treatment, where organisms contained in ballast water are killed in a short time without any negative influence on marine environment. This application is a significant step in preventing invasive spread of marine organisms and protecting marine species diversity, offshore environment. However, the technology and crafts of oxygen plasma sources are very complex, their costs and maintenance are high, the theoretical basis for oxygen plasma source is not well developed, and moreover space-time multi-scale structure effect affects the efficiency of plasma source when it is enlarged in size. Due to the above limitations, scale application of oxygen plasma technology is restricted to few fields. This work aims at building large scale, high efficient oxygen plasma source with the support of National Natural Science Foundation of China "Treating invasive spread of exotic organism with gas discharge (60371035)". In this paper, key problems with regard to establishing large scale DBD oxygen plasma source are studied, main contents are divided into three parts as following: dielectric material for DBD, resonance phenomenon of plasma source, oxygen plasma chemical dynamics.Enamel material with excellent dielectric, heat conducting, and mechanical capabilities is prepared by optimizing ingredients of enamel and technology of enamel firing. This material, which is of low cost and reparable, fits into the requirements for large scale DBD oxygen plasma source.Owing to the enlarging of scale, components of plasma source no longer match with each other, resulting in performance descending, high energy cost and more frequent maintenance. It is found through experiment that the reason for mismatching between DBD plasma source and its exiting power supply lies in system resonance, frequency of resonance is determined by the leak inductance of voltage changer of power supply and the equivalent capacity of the dielectric layer in DBD device.Micro-chemical dynamics simulation study on oxygen plasma generated by DBD plasma source is conducted, the influence of inner parameters of plasma on ozone yield is studied by varying electron density, electron mean energy and ambient gas temperature. It is found that rates of ozone generation increase greatly with increasing electron mean energy and electronic concentration. If ozone molecules are under electron impaction for a long time, ozone concentration will drop sharply. According to temporal and spatial non-homogeneous distribution of electrons in DBD microdischarges, we can optimize the plasma source by setting the parameters which affect microdischarge, such as input voltage, frequency or dielectric. The direction of building large-scale oxygen plasma source has been given by above research.