Search

The results from an experimental measurement of the interelectrode gap filling with plasma channels in a pulsed sliding multichannel discharge of opposite polarities in Ne, Ar and Xe are presented and discussed. The experiments are performed at submicrosecond pulse duration (50-800 ns current pulse FWHM) and gas pressures of 30 and 100 kPa, with two discharge cavities of different alumina ceramic substrate thicknesses (0.4 and 0.17 cm) and interelectrode gap lengths (4 and 10.3cm).A comparative measurement at opposite polarities is aimed at getting additional information on the discharge formation mechanism and optimal mode for quasi-uniform plasma sheet generation. The discharge features common for the three gases are revealed. In particular, the index of interelectrode gap filling with plasma channels is shown to depend at each gas type/pressure/cavity on the peak current, along with the discharge voltage, in such a manner that the greater the peak current at a fixed discharge voltage, the greater the gap filling index, independent of the voltage polarity. For the practical purpose of generating a quasi-uniform discharge structure, the lower of the two gas pressures, the positive discharge polarity and the lowest impedance of the power supply chain are preferable. [ABSTRACT FROM AUTHOR]

The dynamics of an atmospheric pressure air discharge in a point-to-plane geometry with a dielectric layer obstacle on the discharge path is investigated numerically for different applied voltages. Whatever the polarity of the voltage applied, first, a streamer discharge of the same polarity ignites at the point and propagates towards the dielectric layer. After the impact on the dielectric surface, the streamer discharge spreads along the upper dielectric surface and charges it positively or negatively depending on its polarity. On the bottom surface of the dielectric layer, charges with an opposite polarity are deposited. Surface charges on both faces of the dielectric layer are shown to have a significant influence on the discharge reignition for a negative applied voltage, but not for a positive one. Furthermore, it is shown that the dynamics of the discharge reignition below the dielectric layer depends on the polarity of the applied voltage at the point electrode. For a positive applied voltage, the reignited discharge is a positive ionization wave propagating towards the grounded plane. For a negative applied voltage, a double headed discharge is observed with positive and negative fronts propagating in opposite directions. Finally, the minimal value of the ionization integral to have a discharge reignition below the dielectric obstacle is found to be less for a negative applied voltage than for a positive one. [ABSTRACT FROM AUTHOR]

In this paper, particle velocity fields inside a plane-to-plane dielectric barrier discharge (DBD) precipitator are investigated using time-resolved particle image velocimetry. The main objective is to analyse the effect of a filamentary discharge on the particle trajectory. A sine wave high voltage (24 kV, 30 Hz) is applied to create a DBD inside a planar gap (6.4 mm) filled with particles with a mean size of about 0.28 um. The time-averaged velocity of the flow in the centre of the channel is about 1 m s[?]1.After the establishment of the discharge several filaments cross the gap, and induce a strong effect on the particle trajectory. During a complete period of the voltage, successive phenomena are observed. Before the first filament propagation, the shape of the velocity profiles is typical of a laminar flow. At the early stage following the filament propagation across the gap, the grey-level images show a sudden disappearance of the particles at the same location where the filament takes place. This is due to the fast precipitation of particles. During the positive half-cycle, the particles migrate mainly towards the grounded electrode due to their positive net charge. At the end of a half-cycle, the polarity of the electric field is reversed then the particles initially charged return towards the channel centre. Consequently, the particles oscillate delaying their collection. [ABSTRACT FROM AUTHOR]