Characteristic Studies On The Discharge With Water Cathode At Atmospheric Pressure

The discharge with a water cathode at atmospheric pressure is an advanced oxidation technology that initiates physical process and chemical process. In general, the physical process produces high electric field, ultraviolet radiation, bubble and Shockwave and the chemical process produces many reactive species such as O3, H2O2,OH etc. The combination of physical and chemical process can degrade organic pollutants in waste water quickly, which has a lot of advantages in high treatment efficiency, low energy consumption, no secondary pollution and so on. In addition, its strong oxidizing in surface treatment of polyene material has potential application value. In this paper, we developed a new pin-water electrode system. The point anode was made of copper wire of1mm in diameter, the tip of which was tapered to～50μm, which was insulated by a20mm diameter Teflon rod except for the tip. The water as a cathode was hold in a quartz bin with a volume of10×10×20cm3that was cascaded to the ground by a copper sheet of90×90mm2at the bottom of the container. By changing the experimental parameters, the effects of water conductivity and gap distance on electrical properties and the discharge morphology have been investigated. The main findings of the paper are stated as follows:(1) The ignition voltage decreased with increasing water conductivity and increased with increasing gap distance.(2) The maximum conduction current had an increase tendency with the increasing water conductivity, but a negative increase with the gap distance.(3) The time for the streamer propagating across the air gap was estimated to be of about50to60ns with a propagation velocity of～1.3×105m/s. It was found that the water conductivity and the gap distance have no significant effect on the propagation velocity of streamer.(4) The maximum diameter at the middle of the spark channel is about1mm, and approximately contracts with a radical velocity of about2.2×103m/s. No significant dependence of the maximum diameter and decay velocity of the spark channel on the water conductivity and the gap distance were recognized.(5) Within the range studied, the electron density in the spark channel is of～1015cm-3and increase with water conductivity at fixed gap distance. (6) The maximum distance that the spark filament propagates along the water surface is10mm to20mm and a negative increase with the increasing water conductivity and gap distance. The number of the spark filament decreases with increasing water conductivity for fixed gap distance.(7) The propagation velocity of the spark filament on the water surface is104-105m/s and be negative related to the water conductivity and the gap distance.