Dielectric Barrier Discharge Structure Research Articles

Atmospheric pressure uniform dielectric barrier discharge (DBD) in a wide air gap initiated from a narrow starting point

Generating a uniform non-equilibrium plasma in atmospheric pressure air has always been a challenge. It is believed that the maximum spacing for generating a uniform non-equilibrium plasma in atmospheric pressure air, whether using AC or nanosecond pulse drive, is 4 mm. Discharges are always non-uniform when the spacing is greater than 4 mm. In this paper, we propose a new type of dielectric barrier discharge structure to address this challenge. The left end of the structure rapidly increases the discharge spacing from 0.5 mm to 6 mm, while the right side of the main discharge gap maintains a uniform spacing of 6 mm. Nanosecond pulse voltage is used to drive the plasma, an ICCD camera is used to capture the image of the plasma during a discharge pulse cycle, which indicates that a uniform plasma within the 6 mm spacing of the main discharge gap is generated. Upon further reducing the ICCD camera’s exposure time to 20 ns, it is revealed that the uniform plasma is formed due to the rapid propagation of the plasma from left to right at a speed of order of 105 m s−1. Due to the small transverse component of the external electric field, this rapid propagation behavior cannot be due to the external electric field. Therefore, this paper further proposes the hypothesis of electric dipole formation leading to this fast propagation. The hypothesis suggests that the charge separation on the surface of the anode forms an electric dipole, which generates a local discharge at its right end. This local discharge further triggers the discharge in the main gap, and the main gap discharge, in turn, forms a dipole due to charge separation again, by repeating this cycle, the plasma propagates rapidly to the right. Further analysis demonstrates that this dipole can indeed produce a strong electric field of up to 41 kV cm−1 at its right end, which is sufficient to induce a local discharge. Moreover, under such a strong electric field, the electron migration rate can indeed reach 105 m s−1. These findings support the plausibility of this hypothesis.

Analysis of plasma plume parameters in physio-chemical processes of RF plasma jet plume direct in water for the inactivation of Enterococcus bacteria

The contamination of Enterococcus bacterium is widely observed in the living environment and water. The decontamination of drinking water from the bacterial pollution is an important issue in water treatment. Here, the inactivation of Enterococcus bacteria is studied by placing the dielectric barrier discharge structure, with the RF discharge frequency of 13.56 MHz atmospheric pressure argon plasma jet, directly in water, whereas the water around the plasma plume was seething and the bubbles produced stirring all liquid volume. The ability to place a plasma jet nozzle directly in water for 10 min while maintaining a steady and uniform plasma plume, besides water temperature, provides the effectiveness enhancement in the inactivation of bacteria. The absorption of UV radiation in water is effective, and the role of UV radiation of plasma plume was mainly responsible for the destruction of peptidoglycan, which is the outer layer of Enterococcus. Then, the presence of electrons and plasma plume in water leads to the formation of hydroxyl, hydrogen peroxide, and other reactive radicals that are involved in chemical reactions, which lead to the inactivation of micro-organisms. The number of bacteria decreases from the initial value of 16 × 105 MPN/100 ml to less than 1.2 MPN/100 ml. The spectra of the plasma radiation, with the plume length 2 cm within the water, have been analyzed via the first nitrogen negative system N2+B−X. The plume temperature was calculated to be about 64 °C, which has a good agreement with water temperature measured by using a thermometer at about 67 °C after 15 min at maximum 200 W input power of the plasma jet.

Compensation of Heat Effect in Dielectric Barrier Discharge (DBD) Plasma System for Radar Cross-Section (RCS) Reduction.

In this study, the problems encountered in radar cross-section (RCS) measurement experiments utilizing a dielectric barrier discharge (DBD) plasma system are examined and an effective solution is proposed. A DBD plasma system generates heat due to the high bias voltage required for plasma generation. The thermal-induced structural deformation of the DBD structure caused by this high voltage and its impact on RCS measurements are analyzed. In addition, techniques for minimizing the thermal-induced deformation and compensation methods for addressing the minimized deformation are proposed. Furthermore, RCS measurements are conducted on two kinds of DBD structures using the proposed method to experimentally demonstrate the improved agreement between the simulation and measurement results. For both structures, the RCS experimental results are in very good agreement with the simulation results, which enables accurate plasma characterization. In conclusion, it can be expected that the proposed method can be used to provide more accurate RCS measurements on various DBD structures that generate high heat.

Ionization wave propagation of a surface dielectric barrier discharge with a flexible-structure plasma sheet

Plasma sources based on flexible substrates are receiving attention due to their unique adaptability to irregular surfaces and large range of plasma coverage, which endows them with irreplaceable advantages in the fields of material processing and biomedical treatment. Numerous studies have been carried out focusing on the application effects of these flexible plasma sources, while their surface discharge characteristics and mechanisms still lack revelation. In this work, a flexible plasma sheet with a surface dielectric barrier discharge structure is realized via a printed circuit board, and its multiple surface ionization wave (SIW) propagation on curved gas–solid interfaces is studied via experiments and 2D fluid simulation models. Qualitative agreement is achieved between the experiments and simulations. It is found that a positive and a negative discharge are generated at the rising and falling edges of the excitation pulse, respectively. In the positive discharge, SIWs originate at the grounded mesh edge and then propagate to the center in a petal-like pattern, which is shaped by the space electric field. Controlled by electron collision reactions, the development of the excited states of N2 and O2 molecules is similar to that of electrons. In the negative discharge, electrons dissipate and no SIW is generated. The evolution of heavy particles shows differences in this period, which is attributed to the disparate rate coefficients of their consumption reactions. Further study shows that when the plasma sheet changes from convex to concave, the electron density and electron temperature above its surface increase, but the petal patterns of the SIW propagation have no variation. The electron density, electron temperature, and electron impact ionization source will rise as a result of the increasing pulse amplitude or the decreasing duration of the pulse rising edge.

Space Sterilization Effect Through High-Density Plasma Ozone Using DBD Device

Atmospheric pressure plasma is generated via electrical discharge under atmospheric pressure, and the electron energy is generally higher than that of other particles such as ions and neutral particles. In this state, the plasma becomes a non-equilibrium state. Plasma ozone is being utilized in several applications such as high-performance sterilization. Dielectrics such as glass, quartz, and ceramics are generally used in dielectric barrier discharge (DBD) devices. Such dielectric layers are advantageous in limiting the amount of supplied electron charge and distributing plasma evenly on the surface of the dielectrics. The target or environment for sterilization is often a complex structure, and the concept of space sterilization needs to be investigated. In this study, space sterilization is demonstrated through a high-density plasma ozone generator using DBD. The plasma ozone reactor realizes a DBD structure by leveraging a ceramic tube dielectric and a stainless-steel pipe-type conductor at regular intervals. A sterilization test was performed on three types of bacteria using the proposed prototype, and 99.9% sterilization was achieved after 2 h. Thus, plasma ozone sterilization can be utilized as a as a space sterilization device with effective performance without deformation of targets is short periods of time.

Energy conversion analysis of ion wind in surface dielectric barrier discharge at low pressure

Ionic wind actuators are widely used in temperature control, food drying, aircraft propulsion, combustion, air purification, and many other fields. The energy conversion efficiency of ion-wind actuator has been low for a long time. In this paper, a lumped parameter circuit model is established for the surface dielectric barrier discharge structure, and the energy conversion path in the discharge process is proposed for the first time. According to the circuit topology, part of the energy loss is calculated. Based on the mathematical calculations of the circuit model, we discovered the possibility of “negative capacitance effect” in the plasma area, and the experimental verified the correctness of the theoretical deduction and prediction. Meanwhile, the results show that the equivalent capacitance of the solid dielectric is equal to the bottom slope of Lissajous graph, and the negative capacitance effect can effectively reduce the proportion of solid dielectric loss and relaxed polarization loss. The negative capacitance effect improves the energy conversion efficiency of the ionic wind exciter, and the maximum increase ratio is about 47.8%. With the increase of voltage, the deviation between the calculated value of theoretical model and the measured value increases gradually, and finally stabilizes at about 41%.

Solid-State Linear Transformer Driver Based on Full-Bridge Bricks

This article proposes a solid-state linear transformer driver (LTD) structure based on full-bridge bricks, which can not only generate bipolar pulses but also avoid the use of additional core reset circuits. The theoretical analysis and experimental results show that a reverse voltage overshoot will occur after each pulse ends if simultaneous conduction strategy is adopted. The phase shift strategy can provide a low-impedance circuit for the primary current to suppress reverse voltage overshoot. An experimental prototype with six modules is implemented. Each module consists of two full-bridge bricks. The prototype can generate bipolar high-voltage pulses with an amplitude of 0–4.2 kV, a pulsewidth of 100–500 ns, and a frequency of 0–10 kHz. The full-bridge LTD can drive the ozone generator with surface dielectric barrier discharge structure.

Potential Application of Pin-to-Liquid Dielectric Barrier Discharge Structure in Decomposing Aqueous Phosphorus Compounds for Monitoring Water Quality.

Here, we proposed a pin-to-liquid dielectric barrier discharge (DBD) structure that used a water-containing vessel body as a dielectric barrier for the stable and effective treatment of aqueous solutions in an open atmosphere. To obtain an intense pin-to-liquid alternating current discharge using a dielectric barrier, discharge characteristics, including the area and shape of a ground-plate-type electrode, were investigated after filling the vessel with equivalent amounts of water. Consequently, as the area of the ground electrode increased, the discharge current became stronger, and its timing became faster. Moreover, we proposed that the pin-to-liquid DBD reactor could be used to decompose phosphorus compounds in water in the form of phosphate as a promising pretreatment method for monitoring total phosphorus in water. The decomposition of phosphorus compounds using the pin-to-liquid DBD reactor demonstrated excellent performance—comparable to the thermochemical pretreatment method—which could be a standard pretreatment method for decomposing phosphorus compounds in water.

Plasma‐on‐Chip: device for non‐thermal atmospheric pressure plasma irradiation to single cells

AbstractWe report an improvement of the Plasma‐on‐Chip device that enables plasma irradiation to single cells. Dielectric barrier discharge structure was introduced and power consumption was reduced to 200 µW. The modification extended the operation time of the Plasma‐on‐Chip device. As long as 10 min plasma irradiation to yeast cells, Saccharomyces cerevisiae was conducted.

Experimental study on the effects of airflow, magnetic field and combination of airflow with magnetic field on nanosecond pulsed dielectric barrier discharge in atmospheric air

An experimental study of the effects of airflow, magnetic field, and combination of airflow with magnetic field on a nanosecond pulsed dielectric barrier discharge (DBD) in atmospheric air is presented. The DBD is generated by an in-house designed DBD structure (a metal rod is inserted into the traditional parallel-plate DBD). The experimental results show that the application of airflow to the DBD can reinforce discharge and improve the discharge uniformity. When airflow increases to a certain velocity, surface discharge can transform into diffuse volume discharge. Moreover, the application of a magnetic field to DBD in static air can also enhance discharge, which is manifested as the enhancement of surface discharge. A similar but more significant effect is obtained in DBD combined airflow with magnetic field. Compared with the DBD with airflow only, the transition from surface discharge to diffuse volume discharge in DBD combined airflow with magnetic field occurs at a smaller airflow velocity. Besides, DBD combined airflow with magnetic field under different pulse repetition frequencies (PRFs) is also investigated. The results show that the minimum velocity required to generate diffuse volume discharge also shrinks with the decrease in PRF. In short, it is easier to generate diffuse volume discharge under the conditions of airflow, magnetic field, and lower PRF. The underlying physical mechanism of the above phenomena is discussed and mainly ascribed to the enhanced ionization by applying airflow, magnetic field, and lower PRF.

Ozone and oxygen atoms production in a dielectric barrier discharge in pure oxygen and O2/CH4 mixtures. Modeling and experiment

This paper describes the results of modeling of a dielectric barrier discharge (DBD). Filamentary structure of DBD is taken into account in the model by introducing the ratio of the cross section area of a microdischarge to the electrode area as a parameter of the model. Discharge and afterglow stages in the gas flow were studied using a zero-dimensional model for a DBD microdischarge channel. The results of modeling are compared with literature data for [O] number densities in a single pulse nanosecond discharge, and with our own measurements of ozone formation in the DBD. Measurements of ozone number density in oxygen and in mixtures of oxygen with methane served as means of validating the DBD model. The best agreement of the calculated and experimental dependences of [O3] number densities on the discharge energy load was observed, when processes involving vibrationally excited ozone were accounted for together with the discharge microstructure.

Branching, spatial periodicity, and confluence of plasma waves propagating in planar micro-dielectric barrier discharge devices

Self-organization of periodic, streamer-like ionization waves in planar microplasma devices having a dielectric barrier discharge structure is observed. In contrast to plasma propagation in arrays of microchannels or microcavities, the ionization waves originate from a single point but rapidly sub-divide into as many as 10 ‘branch’ plasma wave packets that eventually recombine. In less than 70 ns, the self-organization of the spatially-periodic array of co-propagating branches is complete and two successive sets of waves, separated in distance and time by ∼1.8 mm and ∼50 ns, respectively, are generated. The mean propagation velocity of each plasma packet is greater than 70 km s−1 but values as large as 150 km s−1 have been measured. Because the propagation path for all subsequent streamers is established by the first set of plasma packets, the intensity of the second set is noticeably enhanced. The average length of the primary branches is ∼1.5 mm but reaches a maximum of ∼4.5 mm as the wave packets travel an overall distance of 1 cm. These phenomena are interpreted in terms of photoelectron emission from the floor and walls of the shallow dielectric microcavity, induced by radiation from the advancing packets, and the rapid collapse of the sheath of each microplasma owing to the accumulation of charge on the underlying dielectric. The spatial profiles of the propagating plasmas suggest that generating and probing plasma solitons may now be feasible.

Multimethods and Underlying Mechanism for Realizing Uniform Discharge From Patterned Structures by Varying Controlling Parameters

The uniform gas discharge has long been pursued for realizing or improving some practical applications but is difficult to achieve due to the fact that nonuniform discharges are much easier to be generated in most cases. Usually, achieving uniform gas discharge requires sophisticated devices, and the operation is complicated and time-consuming. In this paper, we introduce simple and flexible multimethods for realizing uniform discharge from patterned structures under dielectric-barrier discharge (DBD) systems by varying experimental controlling parameters, and these methods can be employed in combination. The effects of driving frequency, voltage, duty ratio, and magnetic/electric field on glow DBD structure are investigated. It is found that a uniform glow DBD is obtained when frequency, voltage, and duty ratio are either very high or very low and also by the introduction of strong magnetic/electric field. The underlying physics of these methods is consistent as the elimination of a focusing effect of space electrons. It is concluded that the key of achieving uniform discharge is to uniformize the distribution of space charges.

Comparative study on diffuse dielectric barrier discharges excited by unipolar positive versus bipolar pulses in atmospheric air

Diffuse discharges excited by unipolar positive and bipolar pulses can be achieved by a self-designed dielectric barrier discharge (DBD) structure (a metal rod is inserted into a traditional parallel-plate DBD structure) exposed in airflow. For a self-designed DBD excited by unipolar positive pulses, only a primary discharge occurs in a voltage pulse. When the applied voltage is low, a diffuse discharge first appears near the anode. As the voltage further increases, a diffuse discharge appears in a larger area near the anode. Until the applied voltage is high enough, the discharge fills the whole discharge gap. Additionally, there is a priority region around the metal rod for the development of a diffuse discharge. However, for a self-designed DBD excited by bipolar pulses, two separate discharges are observed in a voltage pulse. The primary discharge occurs at the rising front of the voltage pulse, and the secondary discharge (reverse discharge) takes place at the falling front of the voltage pulse. When the applied voltage is low, the diffuse discharge first starts from the priority region around the metal rod placed in the center of the discharge electrode. As the voltage further increases, the diffuse discharge appears in a larger area around the metal rod. The above observations about the different spatial evolutions of diffuse discharge areas excited by unipolar positive and bipolar pulses are mainly ascribed to the difference of a strong local electric field caused by residual charges. This diffuse discharge has potential applications in surface treatment of materials and thin film deposition.

Classification and uniformity optimization of mesh-plate DBD and its application in polypropylene modification

The classification of spatial characteristics and discharge modes of dielectric barrier discharge (DBD) are gaining increasing attention in industrial applications, especially in the field of surface treatment of materials. In this work, gray level histogram (GLH) and Fourier energy spectrum based on the digital image processing technology are applied to investigate the spatial structure and discharge mode of mesh-plate DBD. The coefficient of variation (CV) is calculated to describe the uniformity of the discharge. The results show that the discharge mode of mesh-plate DBD changes from periodic discharge to filamentary discharge when the applied voltage increases from 11–15 kV. Moreover, a more regular spatial structure is obtained under lower applied voltages during the discharge process. It is also found that the apertures of mesh electrodes which are below 1 mm have smaller values of CV compared to plate electrodes, indicating more uniform discharge. Finally, polypropylene is treated by mesh-plate DBD for surface modification. The hydrophilicity is significantly improved as the water contact angle decreased by 64°, and the dyeing depth is also enhanced.

Experimental study on uniformity of dielectric barrier discharge generated by nanosecond pulse in atmospheric air

Dielectric barrier discharge (DBD) with better uniformity, excited by nanosecond pulses, is achieved within 8 mm air gap by using a self-designed DBD structure in airflow. The self-designed DBD structure is characterized by adding a metal rod (MR) in discharge gap, which will produce a local strong electric field and induce surface and volume discharge. It is observed from sequential single periodic discharge images that the uniformity of discharge starts from the electrode edge at the airflow inlet and moves gradually toward downstream under the action of airflow. When the uniformity of discharge is transmitted to a nearby of MR, a stable uniform and symmetrical annular discharge configuration is formed. Besides, that uniform area can be expanded by adding many MRs or MR array in the discharge gap. There is an optimum distance between every two MRs to produce a continuous and maximum discharge area with better uniformity. The above phenomena are mainly ascribed to the change of electric field distribution caused by MR and the charged particles redistribution induced by airflow.

Research on Homogeneous Multilayer DBD Driven by Submicrosecond Pulsed Power at Atmospheric Pressure Air

Multilayer dielectric barrier discharge (DBD) can efficiently enlarge the volume of homogeneous plasma and its interactional surface area with materials in vertical space, which seems attractive to the industry application. In this paper, a new plasma generator of DBD structure which has multilayers of dielectric barrier boards excited by repetitive submicrosecond pulsed power (0 to −100 kV, 130 Hz–1 kHz, pulsewidth 230 ns, and rise time 120 ns) is introduced, and homogeneous plasma has been obtained in atmospheric pressure air. Experiments on high-speed photography with an exposure time of 5 ns have been carried out to the discharge with three layers of dielectric barrier boards with each gap width of 2 mm. It demonstrates that luminance of the discharge distributes uniformly throughout the upper and the lower gaps. Also, the result of the time evolution image of a three-layer DBD is discussed in this paper, which shows that the two layers of luminous intensity keep good consistency with each other, and this indicates that breakdown of each gap layer happens at the same time in a multilayer DBD. A preliminary processing experiment for polytetrafluoroethylene film has been carried out by adopting homogeneous triple-layer DBD plasma. By testing the water contact angle of the polymer surface before and after the treatment, it was found that hydrophilism of the surface and efficiency of treatment could be effectively improved by the processing of each layer of discharge plasma.

Boundary Effect of Planar Glow Dielectric Barrier Discharge and Its Influence on the Discharge Structure**supported by National Natural Science Foundation of China (No. 11175017)

The dielectric barrier discharge (DBD) in the glow regime in neon has been investigated by experiment and two-dimensional (2D) fluid modeling. The discharge was carried out in a planar DBD system with segmented-electrodes driven by square-wave voltage. The results show that the glow DBD originates in the center of the electrode and expands outward to the electrode edge during each half cycle of the voltage, forming a radial structure. The discharge decays firstly in the inner area but sustains longer in the edge area, showing a reversed discharge area. The discharge cannot completely cover the entire electrode surface, but remains a border of non- or weak discharge. The fluid modeling shows a similar result in agreement with the experiments. The simulations indicate that the electric field in the edge area is distorted due to the boundary effect so that the electric field and charge distribution are different from that in the inner part. The distorted field reduces the longitudinal component near the edge and causes the local field to be lower than that in the center, and hence makes the discharge behindhand. It also induces a transverse field that makes the discharge extend radially outward to the edge. The boundary effect plays an important role in the glow DBD structure.

Dielectric Barrier Discharge Structure Design for Sewage Treatment

The problem of the urban water shortage and water pollution is becoming problem more and more serious. Therefore, governments around the world pay close attention to the application of sewage treatment technology, especially that with high efficiency, low energy consumption and strong operability. Dielectric barrier discharge (DBD) can produce low temperature plasma under atmospheric pressure, and the application of the technology for sewage treatment research gradually becomes to be one of hot research. In this paper, the dielectric barrier discharge structure is designed, and the plasma produced is used for sewage treatment research. The system adopts coaxial type discharge structure. The research shows that the structure is safe and reliable. And, it has low discharge power and can discharge uniformly. So, the plasma produced by dielectric barrier discharge can be convenient and easy to used in sewage treatment, and the result is effective.

Influence of voltage magnitude on the dynamic behavior of a stable helium atmospheric pressure plasma jet

Effects of voltage magnitude on the development of a stable helium atmospheric pressure plasma jet are investigated by current measurements and high temporal-resolution streak images. Generated by a coaxial dielectric barrier discharge structure, the entire discharge can be classified into three regions: discharges in the tube gap, downstream jet, and up-streamer. The discharge morphologies of each region are analyzed. In the positive discharge phase, there are two discharges in the tube gap between the electrodes; the first one is ignited as corona and then developed into streamer corona, and the second one is similar with positive glow. The downstream jet is ignited independently from the discharge in the tube gap. Referred as “plasma bullet,” the dynamic behavior of the jet can be well described as a positive streamer. Under specific applied voltage, the jet is found to be composed by double bullets in which case the jet length decreases since that less charge is carried by the first bullet. The up-streamer can be captured as long as the discharge in the tube gap is activated. Propagating with velocity of ∼4 km/s, the up-streamer can be regarded as the extension of the first discharge in the tube gap. In the negative discharge phase, the discharge is confined in the tube gap with nearly symmetrical morphology with the positive one. Besides, with the rising of voltage, the negative discharge is initially intensified and then turns weaker after surpassing certain voltage, which may provide suitable condition for the occurrence of double-bullet phenomenon.