Influence of surface charges on the structure of a dielectric barrier discharge in air at atmospheric pressure: experiment and modeling (original) (raw)
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Plasma Processes and Polymers, 2010
The reported dielectric barrier discharge (DBD) source comprises of a ceramic-covered copper electrode, and plasma can be ignited in ambient air with grounded 'opposite' electrodes or with objects of high capacitance (e.g., human body), when breakdown conditions are satisfied. Filamentary plasma mode is observed when the same source is operated using grounded opposite electrodes like aluminium plate and phosphate buffered saline solution, and a homogeneous plasma mode when operated on glass. When the source is applied on human body, both homogeneous and filamentary discharges occur simultaneously which cannot be resolved into two separate discharges. Here, we report the characterization of filamentary and homogeneous modes of DBD plasma source using the above mentioned grounded electrodes, by applying optical emission spectroscopy, microphotography and numerical simulation. Averaged plasma parameters like electron velocity distribution function and electron density are determined. Fluxes of nitric oxide, ozone and photons reaching the treated surface are simulated. These fluxes obtained in different discharge modes namely, single-filamentary discharge (discharge ignited in same position), stochastical filamentary discharge and homogeneous discharge are compared to identify their applications in human skin treatment. It is concluded that the fluxes of photons and chemicallyactive particles in the single filamentary mode are the highest but the treated surface area is very small. For treating larger area, the homogeneous DBD is more effective than stochastical filamentary discharge. -7.5 -5.0 -2.5 0.0 2.5 5.0 7.5 1E16 1E18 1E20 1E22 Flux of ozone / m -2 s -1 radius of electrode / mm 1 ppm single-filamentary DBD homogeneous DBD stochastic-filamentary DBD Plasma Process. Polym. 2010, 7, 665-675 ß
- Rodrigues et al., 2017, Experimental Characterization of Dielectric Barrier Discharge Plasma
Active flow control by DBD plasma actuators is a topic with great interest by worldwide scientific community. DBD plasma actuators are mainly used for boundary layer control in order to improve the aerodynamic performance of aerial vehicles. These simple devices consists of two electrodes separated by a dielectric barrier material. The actuator operates when is supplied by an AC high-voltage and high-frequency signal. When the amplitude of the applied voltage is large enough, an ionization of the air (plasma) occurs over the dielectric surface. These ionized particles, in the presence of the electric field gradient, produces a body force on the ambient air. In the present study, different experimental techniques are described and used to provide an experimental characterization about electrical parameters, induced velocity and thermal behaviour of DBD plasma actuators. The results are presented and discussed considering the possible applications of DBD plasma actuators. Resumo O controlo ativo de escoamentos, a partir de atuadores a plasma DBD, é um tema de grande interesse para a comunidade científica mundial. Os atuadores a plasma DBD são principalmente usados para controlo da camada limite de modo a aumentar o desempenho aerodinâmico de veículos aéreos. Estes dispositivos de grande simplicidade consistem em dois elétrodos separados por uma camada de material dielétrico. O atuador funciona quando alimentado por um sinal AC de elevada tensão e elevada frequência. Quando a amplitude da tensão aplicada é suficientemente elevada, ocorre a ionização do ar adjacente ao dielétrico (formação de plasma). Estas partículas ionizadas, na presença do gradiente de campo elétrico, produz uma força no ar ambiente. Neste estudo, diferentes técnicas experimentais são descritas e utilizadas de modo a fornecer uma caracterização experimental de parâmetros elétricos, velocidade induzida e comportamento térmico dos atuadores a plasma DBD. Os resultados são apresentados e discutidos considerando as possíveis aplicações dos atuadores a plasma DBD.
Atmospheric pressure plasma of dielectric barrier discharges
Pure and Applied Chemistry, 2000
The dielectric barrier discharge (DBD) has a number of industrial applications and has been a subject of research for many years. Many studies have been carried out to understand the underlying DBD physics. Despite the fact that much progress has been made, some important issues are still far from being clear. In this work, we summarize the basics of DBD physics and introduce innovative concepts of discharge behavior that were discovered recently.
Journal of Physics D: Applied Physics, 2013
We report on experimentally obtained values of the electric field magnitude on a dielectric surface induced by an impinging atmospheric pressure plasma jet. The plasma plume was striking the dielectric surface at an angle of 45 • , at 5 mm from the surface measured at the axis of the jet. The results were obtained using Pockels technique on a BSO (Bi 12 SiO 20 ) crystal. A coaxial configuration of the plasma jet was used, operating in a stable mode with one bullet per voltage period, at 30 kHz and amplitude of 2 kV. The electric field was shown to be a function of the gas flow (He, at 300, 500 and 700 SCCM) and the manner in which the discharge spreads over the dielectric surface. The maximum value of 11.6 × 10 5 V m −1 was obtained at the negative half-period of the discharge current measured at the grounded electrode, at the flow of 300 SCCM. The largest electric field averaged over the area of the spreading of the discharge (3.6 × 10 5 V m −1 ) was found in the same conditions.
Journal of Electrostatics, 2009
Dielectric barrier discharge (DBD) is an important method to produce non-thermal plasma, which has been widely used in many fields. In the paper, a repetitive nanosecond-pulse generator is used for the excitation of DBD. Output positive pulse of the generator has a rise time of about 15 ns and a full width at half maximum of 30-40 ns, and pulse repetition frequency varies from single shot to 2 kHz. The purpose of this paper is to experiment the electrical characteristics of DBD driven by repetitive nanosecond pulses. The variables affecting discharge conditions, including air gap spacing, dielectric thickness, barrier fashion, and applied pulse repetition frequency, are investigated. The relationship between electric field, discharge current, instantaneous discharge power across air gap, and estimated electron density with the length of air gap, dielectric thickness, barrier fashion, and pulse repetition frequency is obtained respectively, and the experimental results are also discussed. In addition, two typical images exhibiting homogeneous and filamentary discharges are given with different experimental conditions.
Uniform and filamentary nature of continuous-wave and pulsed dielectric barrier discharge plasma
2008
observations of atmospheric pressure DBD plasma were conducted through the transparent electrode in Air, Argon, Helium, Nitrogen and Oxygen gasse! at I and 3 itandard liters per minute (slpm) flow rates through the discharge !ap, utilizing three types of excitation waveforms' Three phenomena were IUr.ru.O, (lfplasma f,itaments travelwith the gas at the same speed as the gas for some but nol all gases; (2) propagation of excitation is observed in Nitrogen plasma and the frlament motion has no directional preference with gas flow direction; and (3) oxygen, Nitrogen and Helium plasmas were observed to be rather uniform at least over longer time periods.
Dielectric barrier discharge for multi-point plasma-assisted ignition at high pressures
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2015
Nanosecond surface dielectric barrier discharge (nSDBD) is an efficient tool for a multi-point plasma-assisted ignition of combustible mixtures at elevated pressures. The discharge develops as a set of synchronously propagated from the high-voltage electrode charged channels (streamers), with a typical density up to a few streamers per millimetre of the length of the electrode. In combustible mixtures, nSDBD initiates numerous combustion waves propagating from the electrode. Very little is known about nSDBD at high pressures. This work presents a comparative experimental study of the surface dielectric barrier discharge initiated by high-voltage pulses ( U =±(20–60) kV) of different polarities in air at elevated pressures ( P =1–6 atm). Discharge morphology, deposited energy and velocity of the discharge front propagation are analysed. Differences between the discharges of positive and negative polarity, as well as the changes in the discharge morphology with changing of a gas mixtu...
Journal of Science and Engineering, 2019
This paper reports the electrical behaviors of atmospheric pressure plasma reactor with Dielectric Barrier Discharge (DBD) in air medium. The DBD discharge was generated in air at atmospheric pressure using Disc Electrode Geometry (DEG) reactor powered by ac voltage (0-7kV) at a frequency of 24kHz. The glass plates of thickness 1.0mm and 3.0mm were used as dielectric. The current-voltage characteristics were studied for two air gap of 2.0mm and 3.0mm by varying the applied voltages. The numbers of filamentary micro discharges were found as increased in each half cycle with increase in power. The observations of Lissajous figure of applied voltage versus electric current was used for measuring energy deposited by discharge and also compared with calculated value. Lissajous figures clearly show that the energy deposited by discharge was dependent on applied voltage. The electron density of discharge was measured by power balance method. Electron density was found in the order of 10 17 per cubic meter.
Pulsed positive discharges in air at moderate pressures near a dielectric rod
Plasma Sources Science and Technology, 2016
We study pulsed positive discharges in air in a cylindrically symmetric setup with an electrode needle close (about 1 mm) above the top of a dielectric cylindrical rod of 4 mm in diameter mounted at its bottom on a grounded plate electrode. We present ICCD (intensified chargecoupled device) pictures and evaluations of experiments as well as simulations with a fluid discharge model; the simulations use cylindrical symmetry. In the experiments, there is an initial inception cloud phase, where the cylindrical symmetry is maintained, and later a streamer phase, where it is broken spontaneously. At 75-150 mbar, discharges with cylindrical symmetry are not attracted to the dielectric rod, but move away from it. The dielectric rod plays the sole role of an obstacle that shades (in the context of photoionization) a cone-shaped part of the inception cloud; the cone size is determined by the geometry of the setup. The material properties of the dielectric rod, such as its dielectric permittivity and the efficiency of the photon induced secondary electron emission do not have a noticeable effect. This is due to the abundance of photoionization in air, which supplies a positive discharge with free electrons and allows it to propagate along the electric field lines. Using some simple field calculations, we show that field enhancement due to dielectric polarization does not play a significant role in our geometry as long as the discharge maintains its cylindrical symmetry. The field component towards the rod is insufficiently enhanced to cause the discharge to move towards the rod. Any additional electrons produced by the dielectric surface do not influence this discharge morphology. This interpretation is supported by both experiments and simulations. At higher pressures (400-600 mbar) or for larger gaps between the needle and the dielectric rod, the inception cloud reaches its maximal radius within the gap between needle and rod and destabilizes there. In those cases, streamer channels are more likely to turn into a surface streamer. All our experiments and simulations were performed at moderate pressures (75-600 mbar), but we expect that the results will be the same for other pressures assuming that all the lengths scales (including the rod) in the setup are rescaled according to the Townsend scaling of the discharge.
The Transition Between Different Discharge Regimes in Atmospheric Pressure Air Barrier Discharge
Contributions to Plasma Physics, 2007
Key words APG in air, diffuse barrier discharge, OAUGDP. PACS 52.80. Hc, 52.50.Dg In our previous work [1], we have demonstrated the possibility of observing the transition from a filamentary dielectric barrier discharge operation regime into the diffuse barrier discharge regime in air at atmospheric pressure. This work presents our attempt to reproduce the transition conditions in newly constructed transparent discharge reactor. The role of appropriate power supply and dielectric barrier to stabilize the discharge in a Townsend-to-glow discharge region is investigated and discussed. Unlike operating in nitrogen, a streamer mechanism is involved in the formation of the uniform air plasma. Nevertheless the electrical current waveform of a diffuse streamer pulse differs from the filamentary streamer pulse, as the diffuse mode pulse exhibits an extended tail part.