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Recently published results of numerical simulations of positive and negative streamers propagating in uniform applied electric fields in air are analyzed in the framework of an analytical approach. It is shown that obtained approximate relations between the streamer radius, velocity and length, depending on the value of applied electric field, are in reasonable agreement with the computational data. • Characteristics of streamers propagating in uniform electric fields are considered. • Analytical approach to evaluation of streamer parameters is developed. • Linear relations between the streamer radius, velocity and length are obtained. • Comparison of analytical results with available computational data is performed. [ABSTRACT FROM AUTHOR]

Results of simulation of streamers propagating along atmospheric-pressure air plasma jets formed by pulsed discharges in thin dielectric tubes are presented. The specific feature of these jets is substantial gas heating by the discharges. The hot gas, emerging from the tube, is cooled at mixing with surrounding air. The streamers are guided along the jet axis, the channel with reduced gas density. Spatial profiles of various plasma parameters inside the jet are calculated. The densities of produced oxygen and nitrogen atoms near the jet axis are one-two orders larger, while the widths of radial profiles of these species are several times smaller than those in typical helium plasma jets. [ABSTRACT FROM AUTHOR]

Results of experimental and computational study of the dynamics and structure of atmospheric-pressure air plasma jets formed by barrier discharge in a thin dielectric tube are presented. Formation of plasma bullet-guided streamers, moving along the jet with velocity varying in the range (1–3) $\times 10^{{\mathrm {7}}}$ cm \text{s}^{{\mathrm {-1}}} , is observed. Simulation, for conditions of the experiment, gives the streamer radius, velocity, and propagation length in reasonable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Results of simulation of positive streamer propagation in atmospheric air, obtained in the framework of a 2-D fluid model, at various rise times of applied voltage pulses are presented. It is shown that the variation of the rise time allows one to control the streamer characteristics: the streamer widths, propagation velocity, densities of charged and excited neutral species, and electric current. At very short (subnanosecond) rise times, it is possible to obtain wide streamers, carrying large currents and producing considerable amounts of reactive species. [ABSTRACT FROM AUTHOR]

Estimates for the discharge initiation voltage in hydrocarbon liquids in point-plane gaps are obtained, basing on evaluation of the ionization integral describing electron multiplication in avalanches in liquids. An approach for estimation of the voltage required to inception of filamentary streamers is presented. It assumes that, like in gases, a minimum radius of streamers propagating in liquids exist. It is shown, in agreement with published experimental data for cyclohexane and pentane, that at point radii smaller than some threshold value (of several micrometers) the discharge initiation voltage is lower than the voltage of inception of filamentary streamers. At point radii exceeding this threshold, filamentary streamers occur just at the discharge inception. [ABSTRACT FROM AUTHOR]

CO2 is a possible alternative to SF6—which has a high global warming potential—as the interruption medium in gas circuit breakers. The performance of CO2 is investigated in this paper by carrying out experiments in representative test devices and by performing computational fluid dynamic (CFD) simulations; some comparisons with SF6 and air are given. It is found that the thermal interruption performance of CO2 is lower than that of SF6, but higher than that of air. The measured dielectric recovery after arcing is compared for CO2 and SF6; a streamer model is used to calculate the breakdown voltage in CO2; good agreement with measurement is found. The speed of sound and the adiabatic coefficient, important parameters that influence pressure buildup and gas flow, are compared for SF6, CO2, and air. CFD simulations of the pressure buildup in CO2 and SF6 both illustrate the qualitative differences between the two and show good agreement with measurements. [ABSTRACT FROM PUBLISHER]

The numerical results on naphthalene removal in biogas are presented and compared with experiment. Plasma-chemical processes in discharge and postdischarge stages are considered. The self-consistent approach for modeling of cleaning process on the basis of pulsed corona discharges is demonstrated. It has been revealed that the reaction of naphthalene (C10H8) with excited nitrogen molecule (N2 (A³Σ)) is very important in the cleaning process in nitrogen-containing mixtures. The addition to N2 of CO, CO2, and H2 results in the deterioration of treatment. [ABSTRACT FROM AUTHOR]

Presents information on a study that developed a model of atmospheric-pressure air discharges sustained by electromagnetic surface waves. Description of the model; Results and discussion on the study.

The characteristics of an atmospheric pressure, RF discharge in air were determined and compared with a 2D numerical model adapted from that used for a dc glow discharge. For a 15 mm discharge, the RF plasma's electrical and optical characteristics show a close correlation to several equivalent dc plasmas and to the results calculated from the adapted model. For an rms conduction current range of 11–30 mA, the rotational temperature varies between 2800 and 3200 K; the vibrational temperature shows a change of 3500–4000 K with near equilibrium conditions to the rotational state occuring in the central region of the discharge. Spatial measurements and modelling of nitrogen emission spectra identify the changes in the temperatures and dimensions along the vertical z-axis as well as the spatial dependence on the atomic and molecular species generated in the discharge. [ABSTRACT FROM AUTHOR]