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Abstract: In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by nanosecond pulsed high voltage are investigated. The goal is to experimentally characterize the surface DBD actuators in terms of electrical and geometrical parameters. The actuators are made of two conducting electrodes separated by a thin dielectric (Kapton films) and arranged asymmetrically. The active electrode is connected to a pulsed high voltage power supply (voltage up to ±10 kV, rise and fall times of 50 ns and pulse width of 250 ns) and the second electrode is grounded. The experimental results show that the energy per pulse (normalized by the length of the active electrode) is smaller when one increases the inter-electrode spacing between 1 and 3 mm, the thickness of the dielectric barrier between 120 and 360 μm or the length of the electrodes between 10 and 50 cm, for both applied voltage polarities. Optical characterization of the plasma layer for different electrode gaps has been investigated by using an ICCD camera. Results indicate that the plasma produced by positive and negative rising voltage propagates in a streamer-like regime with numerous and well-distributed channels, for any electrode gap distance. However, the positive and negative falling voltage produces similar discharges only for large electrode gaps. In this case, the plasma layer starts from a corona spot in contact with the active electrode and expands in the direction of the grounded electrode in a plume shape. [Copyright &y& Elsevier]

The focus of this work has been on the pre-breakdown phenomena and the breakdown characteristics of N gas in a sphere-plane gap under various impulse voltages. Both electrical and optical experimental investigation methods were used. Following parameters were considered: gas pressure range from 0.2 to 0.6 MPa, electric field utilization factor of the electrode configuration 71%, positive and negative impulse waveforms with the rise time of 500 ns, 1.2 μs and 180 μs. The observed discharge processes before the breakdown through the light emission images by the ICCD camera are in good agreement with the streamer mechanism. Under both polarity stresses, discharges are initially concentrated around the tip of the sphere and later pointing towards the earth electrode. However, negative streamers are thinner and more diffuse. As expected, the breakdown voltages for negative polarity are lower than those for positive polarity regardless of the gas pressure and shape of the applied impulse voltage. The breakdown voltage is increased with shortening the rise time of pulse waveforms. As a substitute for SF, N gas under pressures above 0.3 MPa can reach the standard rated withstand voltage for 24 kV C-GIS. [ABSTRACT FROM AUTHOR]

The electrical properties of metal-dielectric-metal (MDM) structures with the dielectric layer representing a monolayer of spherical AlO or ZrO oxide nanoparticles have been studied. It is established that these heterogeneous structures exhibit electric conductivity according to the mechanism for which the differential resistance dU/dI is negative and reversibly approaches zero with increasing current I. The electric conductivity strongly depends on the polarity of the applied voltage U, provided that electrodes are made of basically different metals or the same metal with different surface conditions. The mechanism of the electric conductivity in the given MDM structure depends on the diameter of nanoparticles in the dielectric layer. [ABSTRACT FROM AUTHOR]

This paper reports an experimental study of the optical emission characteristics of the surface dielectric barrier discharge plasma excited by nanosecond pulsed voltage. N2(C3Пu) rotational and vibrational temperatures are almost the same with upper electrode powered with positive polarity and lower electrode grounded or upper electrode grounded and lower electrode powered with positive polarity. While the electron temperature is 12% higher with upper electrode powered with positive polarity and lower electrode grounded. When the frequency is below 2000 Hz, there is almost no influence of applied voltage amplitude and frequency on N2(C3Пu) rotational, vibrational temperature and electron temperature. As the pressure decreases from 760 Torr to 5 Torr, N2(C3Пu) rotational temperature remains almost unchanged, while its vibrational temperature decreases initially and then increases. The discharge mode changes from a filamentary type to a glow type around 80 Torr. In the filamentary mode, the electron temperature remains almost unchanged. In the glow mode, the electron temperature increases while the pressure decreases. [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]