Edge Effect In Dielectric Barrier Discharge

Dielectric barrier discharge (DBD) is a common method to produce low temperatureplasmas which has been used widely in industries. Uniform glow DBD is the best choice formany applications. However there exist various instability and non-uniformity in glow DBDchannels. This thesis focuses on the impact of electrode boundary on discharge structure ofglow DBD.First, the influences of driving voltage and frequency, electrode shape and radial lengthon characteristics of glow DBD are investigated experimentally. The results show that theglow DBD will be patterned under appreciate voltages and ranged frequencies. UniformDBD can achieve at lower or higher frequencies as well as at very high voltages. There existsboundary effect in a limited electrode dimension, characterized by a weak discharge regionnear the edge which increases as the voltage decreasing. Uniform DBD does not developsynchronized over the whole electrode surface. The discharge and current start from thecenter and then extends outwards the edge, with stronger discharge in center while weakerone in the edge area. During the current decay, the discharge stops firstly in the center butlasts longer at the edge, resulting in a reversed discharge image.Then the DBD process is reproduced by two-dimensional fluid modeling and thephysical parameters are analyzed. It is shown that the DBD characteristics depend on theinitial electric field and the space charge distribution. At lower frequency, the DBD startsfrom the center where the field is stronger, and develops outwards the edge. The boundaryeffect of electrode comes from the distortion of the field near the edge. On one hand it reducesthe longitudinal field so that the discharge is weaker and behind the center. On the other handit induces a weak transverse field which makes the electrons being able to accumulate thereduring the discharge. When these charges cannot decay sufficiently to a low or uniform state,the relative denser electrons may cause the discharge starts in this area ahead of the center athigher frequency, causing a kind of activation-inhibition effect of the discharge under non-uniform charges. This finally results in a patterned DBD under suitable voltages.