[en] The propagation of the front of a single surface dielectric barrier microdischarge is studied using an analytical model based on the charge balance equation. The model allows one to find analytical dependences of the discharge propagation velocity and the length of the discharge zone on the parameters of the dielectric barrier and applied voltage pulse. To solve the problem, the results of numerical simulations of the distributions of the electric field, potential, and electron density along the discharge channel are used. The results obtained with the help of the proposed model agree qualitatively with available experimental data.

[en] The thrust induced by a set of microdischarges forming a surface dielectric barrier discharge (SDBD) at sinusoidal alternating voltage is estimated analytically by a phenomenological model based on available experimental data and achieved understanding of SDBD physics. Qualitative coincidence between theoretical predictions and experimental observations for thrust dependence on voltage at different dielectric thicknesses and its relative permittivity is demonstrated by the developed phenomenological model. The volumetric force is primarily induced by the negative voltage half-cycle. The origin of the force is the accumulation of volumetric negative charge carried by negative long-lived O₂^- and O₃^- ions. This accumulation is proportional to the third power of discharge length giving a strong force dependence on applied voltage. The directions of further SDBD investigation and actuator performance improvement are discussed. (paper)

[en] A physical and numerical model for surface dielectric barrier discharge evolution in atmospheric air was developed and tested against experimental data for discharge parameters. Both discharge formation and relaxation phases were simulated successfully using a new approach of non-local air ionization by electron impact and ab initio boundary conditions on the electrode and dielectric surface. The main features of the physical and numerical model of the discharge simulation have been discussed. It was shown that discharge relaxation phase contributes primarily to momentum and heat sources relevant for flow control. The momentum source spatial distribution has a complex structure with the regions of upstream and downstream body force direction and qualitatively depends on applied voltage polarity and voltage pulse waveform. For different conditions it could lead to either near-surface flow acceleration or vortex generation.

[en] The dynamics of radiation intensity at 337 nm emitted by the surface dielectric barrier discharge driven by 50 ns duration and 8 kV amplitude voltage pulse of both polarities has been analyzed experimentally and numerically. The calculations were performed in a 2D approach for experimental conditions to check the existing numerical models and understand what processes manage the discharge length and the spatial distribution of the discharge radiation intensity. Experimentally measured and numerically simulated profiles of radiation intensity along the discharge length notably differ from each other and the performed modification of the discharge physical model does not essentially change this difference. Radiation intensity from the discharge channel has been shown to be extremely sensitive primarily to the value of reduced electric field. We suppose that the discrepancy between experiment and numerical simulation could be due to 2D instead of 3D simulation and corresponding incorrect estimation of electric field distribution along the discharge channel. The numerical simulation of discharge length is in good agreement with experiment for the discharge stroke at the leading front of the voltage pulse and gives few times less values for the backward discharge at the trailing edge of the voltage pulse. (paper)

[en] The discrepancies between the quasi-elastic and inelastic approaches to the calculation of the electron and hole mobilities in diamond at low temperatures when the carrier scattering from acoustic phonons becomes significantly inelastic have been numerically estimated. The calculations showed that the mobility described by a close-to-equilibrium distribution function differs several times from that obtained within the quasi-elastic approach even at 20 K. The results obtained are important for interpreting the low-temperature electrical experiments on high-purity diamond single crystals.

[en] Ignition of stoichiometric hydrocarbon : air mixtures by a nanosecond surface dielectric barrier discharge has been experimentally studied at room temperature and atmospheric and subatmospheric pressures. Observations were made for different voltage polarities and shapes of the high-voltage electrode. The ignition delay time and the velocity of the combustion wave were measured in a C_2H_2 : air mixture versus applied voltage by processing discharge gap images. It was concluded that the mixtures are ignited easier by the discharge for a negative voltage polarity and when it develops from a gear-like electrode. A 2D simulation of the discharge was performed to calculate the temporal and spatial distributions of generated active species and gas temperature during the discharge and in its afterglow for both electrode polarities. It was shown that the voltage threshold for ignition by a negative-polarity discharge is lower than that for a positive-polarity discharge, in qualitative agreement with observations. This is due to the formation of a region with efficient active species production and fast gas heating in the immediate vicinity of the high-voltage electrode when a voltage of negative polarity is applied to it. (paper)

[en] This paper presents the measurements of discharge length for surface dielectric barrier discharge driven by single voltage pulses with different voltage slopes (0.05–3.4 kV ns⁻¹) and different amplitudes of the pulses (7–15 kV). The measurements were carried out for different barrier dielectric materials characterized by relative dielectric permittivity ε from 2 to 35 and different thickness (0.8–5 mm). For all the voltage pulses, the discharge has a channeled structure and the discharge length decreases with increased ε value. The discharge length dependence on dielectric thickness is not notable. The comparison of experimental results with predictions of the analytical model leads to the conclusion that for positive voltage pulses, the discharge development occurs as a set of separate 3D streamers rather than a 2D plasma sheet even in the case of maximal considered 3.4 kV ns⁻¹ voltage slope. The measured discharge lengths lay in between the predictions of the 2D and 3D models. (paper)

[en] The ratio of emission intensities of the second positive N₂(C³Π_u, v′ = 0) → N₂(B³Π_g, v = 0), 337.1 nm and first negative N₂⁺ (B²Σ_g⁺,v′=0) → N₂⁺ (X²Σ_g⁺,v=0), 391.4 nm systems of nitrogen have been measured in a nanosecond surface dielectric barrier discharge (SDBD). The measurements were carried out in synthetic air for a pressure range 1–3 bar for different polarities of the high-voltage (HV) pulse. For all the investigated conditions, the ratio of emission intensities at the wavelengthes 391.4 and 337.1 nm, measured experimentally, R_391/337^exp is systematically higher for the positive polarity of HV electrodes. To analyze the spatial distribution of N₂(C³Π_u) and N₂⁺ (B²Σ_g⁺) emissions, comprehensive two-dimensional numerical modeling for P = 1 bar has been performed. The details of the formation of a narrow gap between the dielectric surface and the streamer channel in the case of positive polarity of HV electrodes are discussed. The ratio of integrated over space calculated emission intensities, R_391/337^th, has been analyzed and compared with obtained experimental data. A good agreement was obtained for a negative polarity SDBD. For a positive polarity discharge, R_391/337^exp≫R_391/337^th for all the considered conditions. Explanation for the observed effect is suggested. (paper)

[en] Surface dielectric barrier discharge, initiated by a high-voltage pulse of negative polarity in atmospheric pressure air, is studied numerically and experimentally. At a pulse duration of a few tens of nanoseconds, two waves of optical emission propagate from the high-voltage electrode corresponding to the leading and trailing edges of the high-voltage pulse. It is shown by means of numerical modeling that a glow-like discharge slides along the surface of the dielectric at the leading edge of the pulse, slowing down on the plateau of the pulse. When the trailing edge of the pulse arrives to the high-voltage electrode, a second discharge starts and propagates in the same direction. The difference is that the discharge corresponding to the trailing edge is not diffuse and demonstrates a well-pronounced streamer-like shape. The 2D (in numerical modeling) streamer propagates above the dielectric surface, leaving a gap of about 0.05 mm between the streamer and the surface. The calculated and experimentally measured emission picture, waveform of the electrical current, and deposited energy, qualitatively coincide. The sensitivity of the numerical solution to unknown physical parameters of the model is discussed. (paper)