Model Of Dielectric Barrier Discharge Research Articles

Kinetic model of grating-like DBD fed with flowing humid air

This work proposes a coupled kinetic model to capture the spatiotemporal evolution behaviors of reactive species generated by a grating-like dielectric barrier discharge (DBD) operated in flowing humid air. The coupled model incorporates a zero-dimensional (0D) discharge model for the discharge filament and a 0D kinetic model or two-dimensional (2D) fluid model for the afterglow region. The model is experimentally validated by the ozone measurements under different airflow rates and power levels. With the pseudo-1D plug flow approximation, the spatial distribution of species obtained by the 0D afterglow model agrees well with the 2D fluid model. The kinetics of reactive oxygen and nitrogen species in the discharge and afterglow region and the underlying pathways are analyzed. It is predicted by the model that there exists an optimal discharge power or airflow rate to acquire a maximum density of short-lived species (OH, O2(a1Δ), HO2, etc) delivered to a given location in the afterglow region. The key factor influencing the plasma chemistry is discharge power, regardless of initial species density, and less concerned with pulse width. The proposed model provides hints for a better understanding of DBD-relevant plasma chemistry operated in ambient air.

Non-thermal plasma actuator mechanism in interaction with fluid flow structure for aeronautical flow control

Plasma actuators generated by surface dielectric barrier discharge are developed for controlling flow in aeronautics applications. This research studies the simulation of cold plasma discharge at atmospheric pressure coupled with compressible fluid dynamics using COMSOL Multiphysics 5.4. Modeling of dielectric barrier discharge in air at high voltages is carried out in two dimensions. The development of electric field and space charge density are discussed in several cases to determine the discharge regime. Non-thermal plasma generates tangential ionic winds at the surface during corona discharge. The results are validated by the experimental results of the literature. The maximum electric wind velocity above the actuator grows linearly with the applied voltage, and simultaneously, the horizontal extension of the discharge grows with the applied voltage. The induced electrohydrodynamic force augments with the applied voltage amplitude, reaching saturation at higher voltages. Moreover, as the voltage rises, the discharge becomes filamentary, inducing a higher number of streamer pulses. Hence, the power consumption discharge increases abruptly as the voltage rises. In addition, the efficiency increases at higher voltage amplitudes and with the dielectric thickness. Our findings give a clear description of physical atmospheric plasma parameters in the surface discharge mechanism and the efficiency of the actuator plasma.

Load model and parameter measurement method of DBD for power supply design

Plasma is widely used in sterilization and disinfection, environmental treatment, and material surface modification. At present, the DBD load equivalent circuit model used in the design of dielectric barrier discharge (DBD) low-temperature plasma generator power supply mainly includes the nonlinear clamping model and linear resistance capacitance model, which have advantages and disadvantages in the research and application of DBD load. This paper focuses on the modeling and parameter acquisition method of the RC parallel DBD load linear model, adds measurement capacitance to the discharge load loop, and obtains RC parallel equivalent model parameters by Q-V and I-V Lissajous-Figure analysis. After the experimental data is processed, the simulation circuit model is built by MATLAB/SIMULINK, and the experimental results are compared with the simulation calculation results. They verify the feasibility of the DBD load parameter measurement scheme and comprehensively demonstrate that the DBD load linear resistance capacitance model has important guiding significance in the design of the DBD power supply.

Plane Parallel Barrier Discharges for Carbon Dioxide Splitting: Influence of Discharge Arrangement on Carbon Monoxide Formation

A planar volume dielectric barrier discharge (DBD) in pure carbon dioxide (CO2) for the formation of carbon monoxide (CO) is examined by combined electrical and CO density measurements. The influence of the type of electrode, the barrier material, the barrier thickness, and the discharge gap on the plasma power and the CO formation is analyzed systematically. The electrical characterization by means of charge-voltage plots is based on the simplest equivalent circuit model of DBDs, extended by the so-called partial surface discharge effect and the presence of parallel parasitic capacitances. The stackable discharge arrangement in this study enables one to elucidate the influence of parasitic capacitances, which can be overlooked in the application of such plasma sources. The determination of the discharge voltage from charge-voltage plots and the validity of the so-called Manley power equation are revised by taking into account non-uniform coverage as well as parasitic capacitances. The energy yield (EY) of CO is analyzed and compared with the literature. No correlations of EY with the mean reduced electric field strength or the geometric parameters of the DBD arrangement are observed.

Ozone production in a dielectric barrier discharge in air- and oxygen–methane mixtures. Experiment and modeling

The effect of methane on ozone production in a dielectric barrier discharge (DBD) was studied in mixtures of CH4 with synthesized air and oxygen. It was found that addition of CH4 significantly reduced the number density of ozone other conditions being equal. A DBD model was developed that takes into account the spatial structure of microdischarges and the fact that near the electrodes their filaments transform into surface discharges, where most of ozone is produced. In addition, in air and air–CH4 mixtures the successive microdischarges were considered to occur not randomly in space, but at the same positions on the electrodes or moving with the flow occurring in the same volumes. The measured values of ozone number density downstream of the DBD were compared with simulation results, obtained with this novel DBD model. A good agreement between experiment and calculations was observed.

Numerical analysis of temperature characterization of air gap discharge in solid insulation under power frequency voltage

Air gap defects in solid insulation of power equipment can cause partial discharge. Temperature, as an important characterization of partial discharge, can be used as a criterion for the deterioration degree of air gap defects to some extent. In this paper, the temperature characterization of air gap discharge is studied. A plasma-kinetics-based dielectric barrier discharge model is constructed. The calculation method of air gap discharge heat source under power frequency voltage is presented. Moreover, the influence of voltage amplitude and gap thickness on temperature is studied. Obtained results indicate that under the power frequency voltage, Joule (Ohmic) heat contributes 90% to the heat source, and O4+ and O2+ and electron e are the main contributors to Joule (Ohmic) heat. O4+ is also the dominant ion in the mixed gas. As the discharge progressed, O4+ almost all clustered near the instantaneous cathode. The O2+ density generally depends on the electron density, but compared with the electron, the spatial distribution of O2+ density is slightly shifted to the instantaneous cathode. The discharge heat source is positively correlated with the air gap thickness and the voltage amplitude. With the increase in air gap thickness, the rising rate of heat sources will also increase. However, when the voltage is 10 kV, the heat source increases first and then decreases with the increase in the air gap thickness. The discharge does not occur when the air gap thickness reaches above 4 mm. This study provides theoretical support for identifying the deterioration degree of air gap defects from the view of temperature.

Using invasive and non-invasive methods to evaluate the therapeutic effect of dielectric barrier discharge (DBD) Plasma in skin graft surgery

Skin graft is effective method to reconstruct large lesions on the skin. Long-term injuries such as burns, skin ulcers, skin flaps, skin grafts... can affect the health of the patient. Skin plays a very important role because it protects the body from dehydration, helps regulate temperature, helps prevent pathogenic bacteria or viruses from entering the body and minimizes skin deformation. In recent years the cold plasma has been used to aid the treatment of chronic skin wounds, burns, ulcers,... To assess the effectiveness of the wound healing process of Plasma, this study uses non – invasive (assess the shrinkage of the wound, the temperature change of the wound) and invasive methods (regeneration of skin tissue structure) to evaluate the therapeutic effects of Dielectric Barrier Dissections Plasma (DBD Plasma) in skin graft surgery. Experimenting with the entire skin graft model on mice, this use of DBD Plasma treatment along with clinical evaluation methods, this is to compare wound healing time between wounds treated with plasma DBD and untreated wound. After 21 days of experimentation, evaluation methods and results processing tools, it was shown that wound healing of skin lesions on mice of the wound area treated with DBD Plasma faster than nontreatment about: (1) The surface shrinkage rate is about 25%; (2) The average wound temperature is less than 0.5-1oC; (3) Healing time is faster from 5 to 6 days. Therefore, DBD Plasma is able to be a potential treatment for wound healing combined with skin graft surgery in the future. The initial study of DBD model is the premise from which could be broader in other animals such as rabbits and pigs with skin structure closer to the human skin. And further, the DBD Plasma shows the potential for preclinical application to human skin graft.

Temporal evolution of OH density in a pulse‐modulated surface microdischarge

AbstractLaser‐induced fluorescence was used to determine the absolute OH density in a pulse‐modulated atmospheric‐pressure surface microdischarge in helium. Measurements were carried out during the discharge and post‐discharge in both plasma layer and downstream region. Experimental findings show that dissipated power, modulation on‐time duration, and the distance from the dielectric surface have more significant effects on the OH(X) lifetime than OH(X) density. The lifetime dependence on power is more pronounced as compared with the modulation duration. Moreover, a dielectric barrier discharge model was presented to estimate the density evolution and loss mechanisms of OH radicals. The results indicate that the decay of OH density is mainly due to the transport process and recombination reactions.

A multi-stage model for dielectric barrier discharge in atmospheric pressure air

A multi-stage model for dielectric barrier discharge in atmospheric pressure air

Electrical modeling of dielectric barrier discharge considering surface charge on the plasma modified material**Project supported by the National Key R&D Program of China (Grant No. 2018YFB0904400), the National Natural Science Foundation of China (Grant No. 51977187), the “Science and Technology Innovation 2025” Key Project of Ningbo City, China (Grant No. 2018B10019), the Natural Science Foundation of Zhejiang Province, China (Grant

We present the variations of electrical parameters of dielectric barrier discharge (DBD) when the DBD generator is used for the material modification, whereas the relevant physical mechanism is also elaborated. An equivalent circuit model is applied for a DBD generator working in a filament discharging mode, considering the addition of epoxy resin (EP) as the plasma modified material. The electrical parameters are calculated through the circuit model. The surface conductivity, surface potential decay, trap distributions and surface charge distributions on the EP surface before and after plasma treatments were measured and calculated. It is found that the coverage area of micro-discharge channels on the EP surface is increased with the discharging time under the same applied AC voltage. The results indicate that the plasma modified material could influence the ignition of new filaments in return during the modification process. Moreover, the surface conductivity and density of shallow traps with low trap energy of the EP samples increase after the plasma treatment. The surface charge distributions indicate that the improved surface properties accelerate the movement and redistribution of charge carriers on the EP surface. The variable electrical parameters of discharge are attributed to the redistribution of deposited surface charge on the plasma modified EP sample surface.

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.

Electrical modelling of homogeneous and filamentary dielectric barrier discharge at atmospheric pressure

Abstract An electrical model of Dielectric Barrier Discharge (DBD) is proposed to model the homogeneous and filamentary discharge. In the first part, for the homogeneous discharge, an equivalent circuit based on the electrical behaviour of DBD is studied. The discharge current and the gap voltage signals are given as a result of model simulation. The analysis of charge transfer has been carried out by means of Lissajous figures, and the dynamic of the discharge is depicted by the discharge characteristic. In the second part, for the filamentary discharge, the randomness of streamers breakdowns and the high frequency of the current pulses have been modelled based on a statistical study of breakdowns distribution. The results of the simulation for the two modes of discharge will be compared to the experimental outcomes.

Atmospheric pressure dielectric barrier discharge involving ion-induced secondary electron emission controlled by dielectric surface charges

Secondary electron emission (SEE) induced by interaction between positive ion and dielectric surface is essential physical process for maintaining sustained discharge and controlling the characteristics of atmospheric pressure dielectric barrier discharge (DBD). In this work, SEE is described based on Auger neutralization theory. Dielectric energy band structure and defect energy level, including hole and electron trap energy levels, are taken into account to build a hypothetical relationship γi = f (σ) between secondary electron emission coefficient γi and surface charge density σ. With the introduction of γi = f (σ) in DBD model, the characteristics of DBD are discussed in both first and steady discharges. It is found that, in steady discharge, γi has higher value during the beginning and development state of discharge pulse of DBD, and γi decreases in extinction stage. The negatively charged dielectric surface enhances SEE before discharge, which benefits the formation of diffuse discharge, compared with DBD of constant γi. Moreover, the increase of energy band gap of dielectric reduces γi, leading to the contractive discharge in DBD. The relationship between γi and σ can be further applied to study the influences of defect energy level parameters on SEE and DBD characteristics.

Comparative experimental analysis of ozone generation between surface and volume DBD generators

Ozone generation by dielectric barrier discharge (DBD) is widely used in industry. Several DBD configurations can be used to generate ozone, which are classified in two main types depending on the geometry of the electrodes: volume DBD and surface DBD models. The aim of this work is to conduct a comparative experimental analysis between surface DBD and volume DBD ozone generators having a cylindrical geometry. This comparative investigation is carried out not only in terms of ozone concentration and energy efficiency, but also in terms of cooling performance. Two experimental setups were used in this work, one for measuring the ozone concentration (in mg/L) and the ozone rate production (in g/h) and a second for cooling experiments. The obtained results show that although the volume DBD model is the most frequently used in industry, the surface DBD reactor gives better results in terms of ozone rate production and cooling.

Investigation of the Flow Structure on a Flat Plate Induced by Unsteady Plasma Actuation with DNS Methods**supported by the Foundation for Innovative Research Groups of National Natural Science Foundation of China (No. 51121004) and National Natural Science Foundation of China (No. 50976026)

An investigation into the flow characteristic on a flat plate induced by an unsteady plasma was conducted with the methods of direct numerical simulations (DNS). A simplified model of dielectric barrier discharge (DBD) plasma was applied and its parameters were calibrated with the experimental results. In the simulations, effects of the actuation frequency on the flow were examined. The instantaneous flow parameters were also drawn to serve as a detailed study on the behavior when the plasma actuator was applied to the flow. The result shows that induced by the unsteady actuation, a series of vortex pairs which showed dipole formation and periodicity distribution were formed in the boundary layer. The production of these vortex pairs indicated a strong energy exchange between the main flow and the boundary layer. They moved downstream under the action of the free stream and decayed under the influence of the fluid viscosity. The distance of the neighboring vortices was found to be determined by the actuation frequency. Interaction of the neighboring vortices would be ignored when the actuation frequency was too small to make a difference.

Numerical modeling of coanda effect in a novel propulsive system

Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system “A.C.H.E.O.N” (Aerial Coanda High Efficiency Orienting jet Nozzle) which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1) High speed jet mixing speeds (2) Coanda effect control by electrostatic fields (3) Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD) plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD) plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS). A numerical method based on finite volume formulation (FVM) was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.

Two-dimensional numerical modeling of interaction of micro-shock wave generated by nanosecond plasma actuators and transonic flow

The influence of nanosecond pulse-driven, surface-mounted dielectric barrier discharge (DBD) actuators on a transonic flow is studied numerically. An airfoil representing turbomachinery blades in transonic flow is considered as a test case. A two-dimensional fluid model of DBD is used to describe the plasma dynamics. The model couples fluid discharge equations with compressible Navier–Stokes equations. Simulations were conducted with an airfoil of NACA 3506 profile in a transonic condition of M=0.75. When a nanosecond pulse voltage is used, with a rise and a decay time of the order of nanoseconds, a significant amount of energy is transferred in a short time from the plasma to the fluid, which leads to the formation of micro-shock waves and therefore to the modification of flow features. Moreover, a plasma energy deposition model is developed and presented by using the results of the plasma discharge model.

Surrogate modelling for characterising the performance of a dielectric barrier discharge plasma actuator

The dielectric barrier discharge (DBD) plasma actuator offers promising opportunities for flow control because of its fast response and non-moving parts. In this work, surrogate modelling is adopted to better understand the impact of the materials and operational parameters on the actuator performance, and to provide an efficient approach for performance estimation. The DBD model based on 2-species helium chemistry engages three design variables: operating frequency, polarity (positive/negative) time ratio of the applied voltage and the dielectric constant of the insulator. Two objectives are identified: the net force generated and the power requirement. Multiple surrogate models are used, which identify two branches of the Pareto front with opposite net force direction and substantially different parametric sensitivities. Global sensitivity analysis indicates that the voltage frequency and polarity ratio are important in different regions of the design space, while the dielectric constant is always important.

Characterizing uniform discharge in atmospheric helium by numerical modelling

One-dimensional fluid model of dielectric barrier discharge (DBD) in helium at atmospheric pressure was established and the discharge was numerically simulated. It was found that not only the spatial distributions of the internal parameters such as the electric field, the electron density and ion density are similar to those in a low-pressure glow discharge, but also the visually apparent attribute (light emission) is exactly the same as the observable feature of a low-pressure glow discharge. This confirms that the uniform DBD in atmospheric helium is a glow type discharge. The fact that the thickness of the cathode fall layer is about 0.5 mm, much longer than that of a normal glow discharge in helium at atmospheric pressure, indicates the discharge being a sub-normal glow discharge close to normal one. The multipulse phenomenon was reproduced in the simulation and a much less complicated explanation for this phenomenon was given.

Modeling of dielectric barrier discharge plasma actuator in air

A detailed physical model for asymmetric dielectric barrier discharge (DBD) in air at low voltages (1.5–2 kV) is developed. Modeling of DBD with an applied sinusoidal voltage is carried out in two dimensions. The leading role of charging the dielectric surface by electrons in the cathode phase is shown to be critical, acting as a harpoon that pulls positive ions forward and accelerates the gas in the anode phase. The positive ion motion back toward the exposed electrode is shown to be a major source of inefficiency in the sinusoidal or near-sinusoidal voltage cases. Based on understanding of the DBD physics, an optimal voltage waveform is proposed, consisting of high repetition rate, short (a few nanoseconds in duration), negative pulses combined with a positive dc bias applied to the exposed electrode.