Enhancement of positive pulsed corona by dielectric enclosure

Abstract

In this work, the effect of positive pulsed corona enhancement by introducing Teflon dielectric enclosure in vicinity to the electrode assembly was studied. The discharge operating in air without the dielectric was able to operate within a very narrow voltage range of approximately 200 V. The pulsing frequency was below 1.2 kHz and current peaks were below 14 mA. Increasing the applied voltage onto the positive electrode beyond this range would result in sparks between the electrodes. When the Teflon tube enclosure surrounding the high voltage electrode was used, the window of stable pulsed corona operation expanded up to 3-5 kV. The pulsing frequency increased up to 12 kHz and the current peak level increased to approximately 35 mA. Increasing voltage beyond the point with peak pulsing frequency would result in a drop of pulsing frequency until the discharge pulsations stopped completely. The Teflon enclosure was able to enhance the average power deposited into the discharge from 10 to 220 mWatt. In addition, the product gases of the enhanced pulsed corona were tested to be mostly ozone with traceable amount of NO2. The discharge used about 150 eV and 1950 eV per one ozone molecule and nitrogen dioxide molecule respectively. The reported here plasma source is promising from the power density/compactness standpoint since significant enhancement (>20 times) of the energy deposition to the discharge can be achieved compared to that of conventional positive pulsed corona.