大气压下高压亚微秒脉冲激励产生的介质阻挡放电的实验分析(英文)

An experimental device is used to study the characteristics of dielectric barrier discharge(DBD)plasma excited by high voltage sub-microsecond pulse power in atmospheric air.Glass,polytetrafluoroethene(PTFE)and plexiglass are used as dielectric barrier materials.Comparatively homogeneous discharge is obtained within 130 mm diameter area in atmospheric air using the three dielectric materials with gap distances of 4.5 mm,6.5 mm and 6.5 mm,respectively.There is no filamentary discharge observed by naked eyes or by camera with the exposure time of 0.25 s.Gas gap voltage,discharge current,discharge power density,etc.are calculated by using Liu’s equivalent circuit model for pulsed DBD.These parameters are used to study the DBD characteristics.Typically,current varies from tens of amperes to hundreds of amperes in atmospheric air DBD excited by sub-microsecond pulses.The peak power can reach to MW order of magnitude.The average power surface density of 1.0 W/cm2and the average electron density of 1011cm 3can also be obtained in the discharge.Rotational and vibrational temperatures,approximately 400 K and 2 650 K,respectively,are obtained by using the emission spectrum of the discharge.This is the basic work performed for a better understanding of the characteristics of atmospheric air DBD plasma excited by high voltage sub-microsecond pulsed power source.     

大气压针板介质阻挡放电中微流注、电晕和辉光放电相互转换研究（英文）

To discuss the modes of dielectric barrier discharge(DBD) between needle-to-plane electrodes in air,DBD is generated and observed on a needle-to-plane device at atmospheric pressure air.Fast images of the DBD are taken by using a charge couple device(CCD) cinema with a macro lens,while the electrical and photo-electricity waveforms of the DBD are recorded.The current waveforms show that under an applied voltage of 3 kV,there are numerous short current pulses in both positive and negative half-periods of discharges.However,under 6 kV,there are still the numerous short current pulses in the positive half-periods,but only one wide current pulse in each negative half-period.This difference is also found in the photoelectric signals.The streamer,corona and glow discharges are observed from the images of the discharges at different applied voltages.The structure of glow discharge in the negative period is exactly the same as that of the low pressure glow discharge.However,in the positive period of discharge there is always a streamer.In the negative period of discharge,while the applied voltage increases,the transition from corona to glow discharge is observed.The progress of a transition between streamer and glow discharge at 6 kV during one period is analyzed.The glow discharge appearance is determined by two factors: the discharge current is limited to a certain extent by the dielectric layer; the charges deposited on the dielectric layer during the last half period enhance the intensity of the electric field.At an insufficient applied voltage,the cathode drop leads to no glow discharge,but Trichel pulses.     

大气压下气流中小电流放电及其应用(英文)

The paper reviews the results of investigations of the low-current atmospheric-pressure discharges in gas flow.The attention is focused on the discharges in electrode systems of coaxial plasmatron and of so-called gliding arc.It is demonstrated that a considerable fraction of discharge current is carried by a plasma column operating in a regime of normal glow discharge with occasional transitions to spark.The nature of glow-to-spark transition is discussed.Beside the plasma column,a weakly ionized gas fills in the interelectrode gap and forms a plasma jet at the exit of electrode system.The jet contains the active chemical particles that play important role in different discharge applications.The applications in plasma assisted combustion systems,for surface treatment with a usage of plasma jet,and for biology and medicine are considered.     

在共面介质阻挡放电中大气压等离子体射流的特性(英文)

Non-thermal plasma jet at atmospheric pressure has recently attracted lots of attention because of its applications in plasma bullet or plasma plume.Thus,we studied on generating plasma jet by coplanar dielectric barrier discharge in a device driven by sinusoidal voltage.The processes of plasma discharges in both positive and negative half cycles were recorded using a high-speed ICCD(intensified charge-coupled device)camera;based on the results we estimated the velocity of plasma propagation,and investigated the influence of gas flow on the plasma development.It is shown that the plasma bullets,which have velocity in the order of 103～104m/s,exist only outside the cathode.APPJ(atmospheric pressure plasma jet)is created by the electron beam from the cathode,and then sustained by a strong radial electric field near and outside the cathode.The gas flow influences the APPJ length in air but not the APPJ discharge,while the discharge is affected significantly by the applied voltage.     

不均匀电场下加压气体中弥散放电和火花放电的形成(英文)

Diffuse and spark discharges are formed and studied during breakdowns with nonuniform electric field in nitrogen,air,and argon at elevated pressures and pulse repetition frequency of 400 Hz.Negative-polarity voltage pulses of the amplitude 20 kV,width at the base of 15 ns and rise time of 2 ns are applied to the electrode with a small radius of curvature.In the conditions of generation of runaway electron beams and X-rays,a CCD camera records the time of the diffuse discharge formation and its duration prior to its transition to a spark one.In all three gases,the diffuse discharge is formed during the time not exceeding 1 ns,when the bright spots appear on cathode in argon and air resulting in the beginning of the spark channel propagation.     

惰性气体对氧气介质阻挡放电臭氧生成的影响(英文)

This paper reports the results of an experimental study of the effect of inert gases He,Ar and Kr on ozone generation in a Dielectric Barrier Discharge(DBD) fed by pure oxygen.The chemical reaction mechanisms related to the process of ozone generation are discussed.The experimental results show that ozone concentration decrease with decreasing oxygen content in all He+O2,Ar+O 2 and Kr+O 2 mixtures mainly owing to the decrease of oxygen content.The conversion ratio of oxygen into ozone increases with increasing oxygen content in He+O2 mixtures,but the addition of Ar and Kr can improve the conversion ratio due to the increase of free electrons density and excited oxygen molecules required for ozone formation through ionization and Penning effect.The effect of Kr is more significant for the lower first ionization energy of metastable state compared with other gases.It is probable that the ozone concentration,and ozone production efficiency increase with Kr addition when the reduced electric field and mean electron energy are high enough.     

脉冲常压空气等离子体转动温度的光谱诊断

Dielectric barrier discharge(DBD) attracts lots of attentions for its great application promises,and the rotational temperature is one of its mostly important parameters.In order to measure the rotational temperature of a pulsed DBD in atmospheric air,the temperature is studied by using optical emission spectroscopy(OES).The discharge is excited by a high voltage pulse with 124 ns rise time and 230 ns full width at half maximum(FWHM) at a repetition rate of a few hundred hertz.The rotational temperatures are studied using different voltages,different repetition rates of the pulse power supply,and different gaps between dielectrics: They are in the range from 390 K to 500 K during the whole discharge.When the gap between dielectrics increases,the rotational temperature initially decreases and then increases.The rotational temperature changes complexly when the pulse repetition rate changes.When the voltage increases,the rotational temperature always decreases,which is not expected.These results allow one to predict the rotational temperature at different supply power parameters and electrode configurations,which is useful for the DBD’s industrial application.     

电晕放电脉冲电流波形和相位分布的测量、分析与仿真(英文)

Partial discharge(PD) is one of the most important phenomenon in high voltage insulations.In most cases, the appearance of partial discharges is related to insulation defects.Understanding partial discharges is important for diagnosis on insulation condition.Corona discharges appear when extremely high electric field appears on the conductor surface exceeding the electric field strength of the gas.The high electric field may occur at around protrusion with very sharp tip.This paper reported a holistic approach of corona discharge investigation.The needle-plane electrode system was used.The medium between the electrodes was air.The needle was made from steel with radius of curvature of 3μm(Ogura needle).Sinusoidal as well as triangular applied voltages were used.The waveform of the corona discharges was measured using a digital oscilloscope.The corona discharge pulses were measured using a phase-resolved PD measurement system.The system was able to measure the magnitude(q) and phase angle position(φ) of each PD pulses,as well as the number of discharge pulses(n).The role of applied voltage was investigated using phase-resolved analysis of corona discharge pulses through pulse sequence,pulse magnitude and pulse number analysis. Experimental results indicated that corona discharge current waveform was an impulse with rise time of about several ns and the impulse width of about 100 ns.The Fast Fourier Transform analysis indicated that the corona discharge current waveform had several spectrum peaks at frequency of 7.8 MHz,85.9 MHz,109.4 MHz and 195.3 MHz.The experimental results also showed that discharge pulses were concentrated around the peak of applied voltage for both sinusoidal and triangular voltages.The discharge magnitude,as well as its probability of occurrence,was strongly dependent on the instantaneous applied voltage.The shape ofφ-n,as well asφ-q-n PD patterns,were strongly reflected by the shape of applied voltage.In order to get deep understanding of the corona discharge,by utilizing results of the phase-resolved analysis,electrical equivalent circuits of corona discharges were proposed.The electrical equivalent circuit contained capacitances and a spark gap.For deeply understanding of PD phenomenon,computer simulation was done by using the proposed electrical equivalent circuits.The similarity of the measured and simulated PD patterns was assessed by comparing measured and simulated theφ-q-n andφ-n PD patterns.The results indicated that simulated PD patterns similar to those obtained from experiment.     

闪电放电通道的等离子体特性（英文）

The plasma characteristics of a lightning discharge channel are reviewed.The spectrum of the natural lightning is investigated by employing the slit-less spectrograph.It is found that the spectrum characteristics are closely related to the intensity of the lightning discharge.The lines in the lightning spectrum are classified into essential lines and characteristic lines,according to the characteristics of lightning spectra with different intensities.The characteristics of the lightning channel and the radiation of the lighting plasma are analyzed in the visible and infrared regions.It is shown that,the visible spectrum of lightning is determined by the radiation generated from the early stage to the development of lightning,while the near-infrared spectrum is determined by the radiation generated after current of lightning reaches the peak.The channel temperature and the electron density are calculated using the information obtained from the lightning spectrum.Both the temperature and the density decrease with the increasing length of lightning channel.Moreover,X-rays and neutrons are produced in the process of lighting mainly due to the pinch effects.     

氩气与氨气混合下的大气压介质阻挡放电(英文)

In this paper,the influence of ammonia admixture on argon discharge properties is investigated.Electrical measurements,as well as ten-nanoseconds-exposure photographs taken by an intensified charge-coupled device(ICCD)camera,are employed to confirm the existence of atmospheric pressure glow discharge(APGD)in Ar/NH3mixture.The breakdown voltage and transition voltage between APGD and filamentary discharge are studied at various ammonia concentrations.The results show that a small amount of NH3can lead to APGD due to the Penning ionization of NH3molecules by metastable argon,and the breakdown voltage increases with the growth in NH3concentrations owing to the electronegative feature of NH3.The optical emission spectrum of Ar/NH3APGD is analyzed.Besides,gas temperature is estimated at 327 K by the diagnoses of the OH(A-X)(0,0)band of the spectrum.     

镀TiO2喷嘴-筒状电极下负脉冲放电等离子体降解酸性橙Ⅱ（英文）

Many sub-products of pulsed discharge,such as ultraviolet light,strong electric fields,shock waves and active species,are effective in treating wastewater.To improve the efficiency of the discharge plasma technology in removing pollutants,adding TiO2 photo-catalyst to pulsed discharges could help.A negative-pulsed-discharge system,which has nozzle discharge electrodes with or without TiO2 coating,is used to degrade azo dye Acid Orange Ⅱ,and the effects of several key conditions(maximum pulse voltage,pulse repetition frequency,initial mass concentration of Acid Orange Ⅱ initial solution pH,treatment duration,the phase of discharge,and the existence of TiO2) on the degradation are experimentally investigated.The degradation of Acid Orange Ⅱ increases with maximum pulse voltage,pulse repetition frequency,and treatment duration,and it is larger when putting the discharge electrode on the solution surface than in air or inside the solution,i.e.the discharge in gas phase is more effective than that in gas-liquid phase or liquid phase.The degradation decreases as the initial mass concentration of the solution increases.It also relates to pH and is higher at acidic conditions than at neutral or alkaline conditions.Compared to treatments without TiO2,the ones using the nozzle discharge electrode with TiO2 coated increase the degradation of Acid Orange Ⅱ by 5 %.It is concluded that the proposed system with TiO2 added in can remove Acid Orange Ⅱ from wastewater effectively.     

大气压氩滑动电弧的光谱诊断(英文)

This work is devoted to the experimental investigation of an AC argon gliding arc discharge at atmospheric pressure.The dynamic behaviour of the argon gliding arc plasma is investigated by the oscillations of the electrical signals,while the time-resolved arc root motion behaviour on the electrode wall is analyzed by high-speed photography.It is found that the anode and cathode arc roots exhibit different motion behaviour on the electrode surface.In addition,emission spectroscopic technique has been employed to determine the axial distribution of the gas temperature and electron density in the argon gliding arc plasma.     

氦气与D2O混合气中阻挡放电灯工作的物理过程（英文）

This paper presents both results of a numerical modeling and an experimental study of the influence of various parameters on the radiation characteristics of barrier discharge lamp working in He/D2O mixture.It is obtained that the intensity of ultraviolet radiation is a non-monotonic function of both the water and the helium pressures.The experimental results also show that the increase of both the discharge voltage and the discharge pulse frequency leads to the increase of radiation intensity.The comparison between the experimentally obtained data and the results of numerical modeling allows us to define the mechanism controlling the ultraviolet radiation in He/D2O mixture at various parameters.     

大气压下柱型微空心阴极放电(英文)

The mechanism of micro-hollow cathode discharge at atmospheric pressure is investigated through simulations using two-dimensional fluid model combined with a transport model for metastable atoms.In the simulations,electric potential,electric field,particle density,and mean electron energy of the discharge are calculated.The results show that the two characteristic regions of the discharge,i.e.cathode drop and negative glow can be distinguished in the simulation.The cathode drop is characterized by strong electric field and high mean electron energy,while quasi-neutral plasma of high density and exists in the negative glow.The peak value of electron density can reach the order of 1017cm-3.The electron temperature varies from several eV to tens of eV.The influence of cathode dimension on the discharge characteristics is also investigated.     

高压太阳能电池阵静电放电效应（英文）

A certain number of charges are deposited on the surface of high-voltage solar array because of effects of space plasma,high-energy charged particles,and solar illumination,hence the surface is charged.Phenomena of electrostatic discharge(ESD) occur on the surface when the deposited charges exceed a threshold amount.In this paper,the mechanism of this ESD is discussed.The ground simulation experiment of the ESD using spacecraft material under surface charging is described,and a novel ESD protecting method for high-voltage solar array,i.e.an active protecting method based on the local strong electric field array is proposed.The results show that the reversal potential gradient field between the cover surface and the substrate materials of high-voltage solar array is a triggering factor for the ESD on the array.The threshold voltage for the ESD occurring on the surface is about 500 V.The charged particles could be deflected using the electric field active protecting method,and hence the ESD on the surface is avoided even when the voltage on the conductor array increases to a certain value.These results pave the way for further developing the protecting measures for high-voltage solar arrays.     

空气中脉冲电压激励的表面微放电特性(英文)

The surface micro-discharge(SMD)excited by pulsed voltage in open air is experimentally studied by measuring its voltage,current,emission image,emission spectrum,and ultraviolet(UV)absorption spectrum.It is found that the SMD occurs intermittently in each cycle,and that it consists of many filaments on the surface of grounded electrode.While the applied voltage’s peak value Up increases from 1.75 kV to 7.25 kV,the discharge area keeps expanding until Up≈6 kV,when the discharge occupies all the available area.The emission spectrum of nitrogen metastable N2(C-B)and the density of ozone increase almost linearly.The ozone density decreases hyperbolically downstream of the grounded electrode due to the diffusion in open air.The characteristics of pulsed SMD are presented and analyzed as well,which may be referred by further investigations.     

外电场及预电离对大功率脉冲氙灯放电等离子体特性的影响(英文)

This work is devoted to experimentally study the characteristics of discharge plasma in high power xenon flashlamps.In the experiments,plasma channel profiles are captured by using a high speed CCD camera,and the radiation energy of the flashlamp is obtained by a pyroelectric energy meter.Voltage and current curves are recorded to shed light on the plasma characteristics.With these diagnostic methods,typical factors influencing the evolution process of plasma channel are studied,including the external electric field and the pre-ionization.The electric potential distribution in the flashlamp influence the plasma channel characteristics the most significantly.The plasma channel pattern for the cases with grounded wires is different from that with ungrounded metal wires.When the wire is ungrounded,it is the coupling voltage between the metal wire and the flashlamp that influences the development of plasma channel.In terms of radiation efficiency,it is proven that there is an optimal interval within 200～300μs between the pre-ionization pulse and the main pulse.     

Effect of Barrier Materials on Discharge Properties in Air at Low Pressure

Dielectric barrier discharge(DBD) is widely investigated in order to obtain uniform low-temperature plasma.Many studies have proved that some barrier materials,especially electrets,can improve the uniformity of discharge.It is regarded as an available way to get atmospheric pressure glow discharge(APGD).In this paper,discharge forms with 4 different barrier materials(alumina,quartz,PTFE and PET) are investigated,and the transition of discharge form depending on the air pressure are recorded to estimate the influence of barrier materials on discharge.By using electrets as barrier materials,homogeneous discharges can be obtained in a more wide pressure range.Under the same experimental conditions,discharges with electrets are more uniform or have larger uniform areas due to the storage and desorption of charges on the surface of electrets.The electrons deposited in the surface layer can be released on next half cycle when the polarity of the applied voltage changes,and provide a number of seed electrons,which makes the discharge more homogeneous.The capacitance and the permittivity of barrier materials have no effect on the discharge form directly.     

沿面放电生成活性物质用于灭活饮用水中大肠杆菌的机制(英文)

Bacterial and chemical contaminations of drinking water imperil the health of people.A reactive species injection method is presented for sterilizing drinking water.To produce reactive species,a gas phase surface discharge reactor(SDR)is designed:a spiral stainless steel wire attached on the inside wall of a quartz glass tube is used as the high voltage electrode,and the drinking water is the ground electrode.The performance and mechanisms of the method in inactivating of Escherichia coli(E.coli)are analyzed.Experimental results show that 500 mL E.coli-contaminated drinking water(108CFU/mL)is completely sterilized within 4 min.Based on the scanning electron microscope(SEM)analysis,there were plasma-induced cell structure damages of the E.coli in the sterilized water,and the damage resulted in the leakage of protein,which was proved by chemical analyses.Meanwhile,the heating effect concomitantly generated by discharge plasma does not influence E.coli inactivation,and the contribution of direct ultraviolet(UV)irradiation could be neglected too.The ozone generated by SDR and the hydroxyl radicals(·OH)subsequently generated in drinking water play the decisive roles in E.coli inactivation because these reactive species cause the cell rupture.     

高压下非均匀电场中局放机理的建模

Partial discharges in air in non-uniform electric field occur in surroundings made of high curvature elements.The equivalent electrode system,needle-plane refers both to external components of high voltage insulating systems and to micro sharpness in the internal structure of those systems.The ionization zone,accumulation of space charge and formation of corresponding current pulses depend on electrode configuration,voltage level,pressure,temperature and humidity of air.The assessment of pressure influence on discharge mechanism in non-homogenous electric field has been performed on the basis of empirical density distributions of discharge charges at different voltage levels,electrode distance,curvature of high voltage electrode and taking into account solid dielectric barrier in serial configuration.The measurement results obtained at variable voltage level yield the influence of electric field strength in the needle electrode zone.While increasing voltage,a deviation from normal distribution may be observed that reveals other forms of discharge.