A Study On Uniform Dielectric Barrier Discharge And Enhanced-corona Discharge At Atmospheric Pressure

The non-equilibrium plasma produced at atmospheric pressure contains a lot of active particles, high-energy electrons and low-energy ions, which can reduce the threshold of chemical reactions. So many reactions can occur in low temperature, even in room temperature. Due to the merits mentioned above, the non-equilibrium plasma is used widely in industrial applications. At atmospheric pressure, the non-equilibrium plasma is usually generated by corona or dielectric barrier discharge. The corona discharge belongs to partial discharge. The merits of corona discharge are that it is stable, easy to sustain and can be driven by DC power supply. However, its shortcomings are also obvious, such as small discharge area, weak current and low efficiency. As for the dielectric barrier discharge, the inhomogeneity is hard to be overcome. So it is very important to develop large-volume, uniform and stable discharge equipments at atmospheric pressure, which is also studied hotly in the whole world.Based on the study on dielectric barrier discharge and multi-pin enhanced corona discharges, the following work is done in the paper.1. The mode transition of dielectric barrier discharge at atmospheric pressure in helium is investigated. It is found that the discharge can transit from one filament to glow discharge by lowering the applied voltage. The discharge mode is determined by the ion density and electrical field. High ion density and low electrical benefit to the formation of glow discharge. Through the analysis of the (0,0) band of the first negative system of N₂⁺ the rotational temperature is calculated by Boltaman plot method and spectrum simulation method, which prove the occurrence of the mode transition. The rotational temperature varies in the range from 300K to 550K, while the vibrational temperature varies from 1600K to 2200K, and the excitation temperature varies from 1200K to 2500K.2. A uniform glow-like plasma is generated in air with a dual discharge device driven by one power supply. The DBD is assisted by the UV illumination from the spark discharge between two pins in series with the DBD. The preionization by the UV irradiation lowers the breakdown voltage of the DBD by yielding adequate seed electrons, which is crucial for obtaining the uniform glow-like discharge. And it is also found that the quick rising time of the voltage on DBD is the other factor in improving the discharge uniformity of DBD. The discharge mode between the two pins will change from enhanced corona to spark if the frequency is up to 4.250kHz.3. Concentric circles patterned air discharge is realized by using a dielectric barrier discharge device. With increasing voltage, the discharge filaments tend to be dense and regularly arranged and the current-voltage waveforms show that the spatiotemporal correlation between filaments is enhanced. Furthermore, the gas flow has great effect on the filaments. The filaments will distribute along the gas flow direction. However, with increasing the density of filaments, this effect of gas flow is weakened.4. In a multi-pin-to-multi-sphere plane DC negative corona discharge configuration, stable and diffuse glow discharge is obtained. The paper investigates the effect of the air gas flow velocity, the gap distance and the electrode structure on the discharge mode transition and the stabilization of the glow discharge by the means of electrical measurements and emission record. The stabilization mechanism of the glow discharge is also discussed. It is found that there is a transitional phase characterized by Trichel pulse with DC component between corona and glow discharge.