Investigation On Some Key Issues In Direct Current Corona Discharge And Design Of Novel Discharge Device

Plasma science and technology are taking more and more important parts in both modern industries and human lives, building the most powerful machines in the world such as an uptodate aerospace craft, making the commodities such as food and suits, cleaning water and air, no matter you concern it or not. Atmospheric the non-equilibrium plasmas carry unique features and characteristics which have provided the base for a host of applications. Unlike the case of the thermal plasmas, these reactions occur without an increase in the gas enthalpy. Because the ions and the neutrals remain relatively cold, the plasma does not cause significant thermal damage to articles they may come in contact with. This characteristic opens up the possibility to use these plasmas for the treatment of heat-sensitive materials including biological tissues. In addition, operation in the high pressure regime lends itself to the utilization of three-body processes to generate useful species such as ozone and excimers.The corona discharge, which can be formed by simple apparatus, is taken as an economical and reliable discharge pattern in many applications, such as particals charging and dust collection from fuel exhausts. But the application of corona discharge is heavily limited by the relatively lower discharge power density. Besides, there are also many doubts in the classical corona physics needed to be clarified. The following researches have been carried out as an attempt to find available solutions of those aformationed problems.1. A detailed comparison investigation between the Trichel pulse and the tuft discharge has been drawn in order to cast lights into the basic progress of pulse formation in the negative corona discharge. It turns out that the Trichel pulse and Tuft discharge pulse are form by the similar physics progress, which could attributed to the negative streamer formation. The existence of a relatively steady negative layer, which results the decay of the Trichel pulse amplitude, has also been proved when the current reaches a threshold value.2. At the same time, the power density variation of muti-pin positive streamer discharge with the different pin spacing has been elucidated by carefully designed experiments. As a result of the former efforts, a new positive streamer discharge based a novel designed sheet electrode has been introduced. Besides, the superiority of this new design compared with the traditional multi-pin case also has been verified. The erosion damages on the surface of the electrode by randomly arc discharge have also been verified by microscope images. A proper ballast resistor in the circuit is also suggested to avoid such damages from happening.3. Electronic excitation temperature diagnosis of DC positive streamer discharge by optical emission Spectrometry based on the sheet electrodes array has been carried out in order to deposit practical materials for potential industrial applications. It turns out that the electronic excitation temperature of DC positive streamer discharge is highly related to the positive ions density and the local temperature variation inside the discharge region. In mixture of oxygen and argon (80% oxygen concentration), the maximum T_exc of 6300 K has been achieved at average current of 600μA. Relative conclusions also include the statement that it is reasonable to keep this discharge burning in a proper lower voltage range for better energy efficiencies and stabilities.4. As an attempt to verify the application possibility in VOC decomposition, a DC positive streamer discharge reactor has been built for further benzene and toluene removal experiment. According to the experiment results, the maximum removal efficiency reaches 68% and 95% for benzene and toluene (the initial density both set at 50ppm, stream flow rate at 10L/min) respectively. The following removal energy efficiency analysis exhibits a good agreement with the relative conclusion in part 3.