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.     

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.     

裸露金属电极中的亚微秒脉冲常压辉光放电（英文）

In order to better understand the physical mechanism of sub-microsecond pulsed glow discharge with bare metal electrodes,using a one-dimensional self-consistent fluid model,the properties of the discharge at atmospheric pressure are numerically studied.The results show that,a discharge without dielectric layers,i.e.a barrier free discharge,is extinguished only with the decrease of the applied voltage.Only one positive discharge event occurs at the slope of the pulsed voltage.A stable glow of barrier free discharge can be achieved only in short durations of the pulsed voltage.The barrier free discharge always starts with a subnormal glow discharge and then evolves into a normal glow discharge.Moreover,to control the discharge stabilization better,the effects of pulse repetition frequency,pulse duration,rising(front) and falling(slope) times on the discharge characteristics are investigated systematically.It is found that the discharge is comparatively more sensitive to the repetition frequency and the pulse duration,while little affected by the rising and falling times.     

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.     

亚纳秒击穿产生超短雪崩电子束过程的动态特性(英文)

In this paper,subnanosecond-pulse and one-nanosecond-pulse generators are used to study the breakdowns in highly overvolted gaps in atmospheric pressure air.With different cathodes,we measured the applied voltage and discharge current to investigate the dynamic characteristics in the subnanosecond breakdown during the generation of a supershort avalanche electron beam.Especially,characteristics of dynamic displacement current are presented in the current paper,which is detected between the ionization wave front and a plane anode.It is shown that during a subnanosecond voltage rise time,the amplitude of the dynamic displacement current can be higher than 4 kA.It is demonstrated that the breakdown in the air gap is assisted by ionization processes between the ionization wave front and a plane anode.     

大气压氦气介质阻挡放电中交流驱动电压频率对击穿电压的影响(英文)

For dielectric barrier discharge(DBD)driven by AC voltage in helium at atmospheric,the relationship between the breakdown voltage and the driving frequency is experimentally investigated using a pair of parallel electrodes.The gap between the electrodes is 1 mm,4 mm,7 mm,and 10 mm,respectively.Meanwhile with an increment of 2 kHz,the applied AC voltage varies from 12 kHz to 30 kHz.In each experiment,the driving voltage increases slowly,till the helium-filled gap breaks down.Based on a number of experimental results and further analyses,conclusions are obtained as follows.(1)For a small gap(1 mm),the voltage that triggers the first breakdown(Uf)is close to the one that sustains steady breakdowns(Us).However,in the larger gaps(4,7,and 10 mm),Uf is obviously larger than Us.(2)For a fixed gap,Uf does not change significantly with the driving frequency,whereas in the gaps except the 1 mm one,Us drastically decreases with the increase of driving frequency.(3)The motion of residual space charges and the dissipation of positive column,two reasonable factors that explains asymmetrical discharges,are also main reasons for the effect of the driving frequency on the breakdown voltages.     

大气压氦气与氩气等离子体射流形成机理的对比研究(英文)

To compare the formation mechanisms of He and Ar atmospheric pressure plasma jets(APPJs),an intensified charge-coupled device(ICCD)are utilized to observe the dynamic process of APPJ.The experimental results show that,He APPJ is first ignited,which is independent of the dielectric barrier discharge(DBD)between the two wrapped electrodes when the high voltage placed at the downstream.The intensity and APPJ length under positive discharge pulses are bigger than that under negative discharge pulses due to the space charge effect.The He APPJ is formed by the DBD development when the high-voltage electrode placed at the upstream side of tube.However,the plasma plume in Ar APPJ is formed by the propagation of DBD whatever the high-voltage electrode is arranged on upstream or downstream side of ground electrode.The difference in formation mechanism between He and Ar APPJs is mainly caused by the gas properties.Moreover,during the discharges,Ar tends to lead to thermal instability and electron Maxwellian instability.     

气压对发电机定子线棒端部电晕放电特性的影响(英文)

According to the mechanism of corona discharge at the end of the generator stator bar,a model of stator bar end corona discharge is presented.In a closed corona cage at low atmospheric pressure,the corona discharge characteristics of the stator bar end model were observed using an ultraviolet imaging instrument and an oscilloscope.The influence of atmospheric pressure on the corona inception voltage and discharge intensity was analyzed.The results show that the corona inception voltage is lower under lower atmospheric pressure;the discharge intensity is stronger under lower atmospheric pressure.The particles swarm-optimized support vector machine was employed to analyze the impacts of air pressure and humidity on the corona inception voltage.Error between the calculated value of the established model and the experimental value is less than 5%.The established model can be used to calculate the corona inception voltage of the stator bar end model.     

SF6对介质阻挡放电臭氧生成的影响（英文）

The influence mechanism of a small amount of SF6 on ozone generation in oxygen or air discharge is investigated.Some results are obtained by probing into the number of the high-energy electrons,which have the sufficiency energy for generating ozone.Introducing a small amount of SF6 into oxygen sharply decreases the number of high-energy electrons,because the electron density decreases sharply while the mean electron energy remains constant due to higher breakdown voltage and lower discharge power,and some high-energy electrons are consumed by the excitation and attachment of SF6.In contrast,when a small amount of SF6 is added into dry air discharge,despite the consumption of the excitation and attachment of SF6,the number of high energy electrons increases sharply,which is attributed to the higher mean electron energy and electron density resulted from higher breakdown voltage and discharge power.When the volume fraction of SF6 increases from 0 to 2.22%,the ozone mass concentration and the ozone yield increase by 45.7% and 29.7%,respectively.Therefore,though the oxygen source should avoid the presence of SF6,adding a small amount of SF6 can improve the ozone mass concentration and the efficiency of ozone generation.     

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.     

Surface Treatment of Polypropylene Films Using Homogeneous DBD Plasma at Atmospheric Pressure in Air

The homogeneous dielectric barrier discharge （DBD） in atmospheric air is most favorable for polymer sur- face modification due to the low cost of operation and the ability of ambient on-line continuous...     

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.     

两相体中正脉冲放电分枝的现象和机理(英文)

Discharge branching is a general phenomenon in atmospheric-pressure air,dense gases,and two-phase mixtures(TPMs).In this work,an ultraviolet imaging device is utilized to investigate the branching of positive pulsed discharges in TPMs.Comparison among the captured images indicates that the branching is caused by the voltages and the macropartilces in the discharge channels combining together.The interaction of macroparticles with ions,electrons or photons is one reason for the branching behavior of pulsed discharges.The generation of electrons at the discharge front closely relates to the work function of dielectric macroparticles,which is a key parameter influencing the electron-emission ability of macroparticle surfaces.The electric field alteration under various applied voltage in TPMs,which is calculated by a two-dimension finite element method,is the other reason for the guiding effect of macroparticles on the streamers compared with in the air.     

基于UV检测的UHV输电线路起晕电压的试验研究(英文)

Corona discharge is being detected by UV imaging detection technology at home and abroad in recent years.This technology is used in the corona tests of conductor bundles in this paper.In order to further research the corona characteristic,optimize geometry parameters and diameter of sub-conductor,and increase corona onset voltage of transmission lines,corona tests of three model conductors which are placed inside the outdoor corona cage are conducted.Corona cage could be used to simulate the corona activities on transmission lines under a low voltage and different conditions in an effective and economical way.Photon which was created by UV light as a result of corona discharge on conductors is detected by the UV detection apparatus.The photon number within unit interval,namely photon counting rate is adopted as the parameter of quantifying the intensity of corona discharge.According to the apparent change of photon number,corona onset voltage can be judged.All tests are conducted under almost same atmosphere condition.Using the method,corona onset voltage is acquired.The results indicate that the tests have a good repeatability,in other words,repeating same test twice same result can be aquired.The corona onset voltage can be acquired exactly from the curve of applied voltage vs.photon counting rate.Therefore UV detection apparatus can not only used to find discharge point exactly,but also applied on corona discharge research and live detection for power equipments.The method using in this paper is proved that is a new available method.     

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.     

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.     

空气中电晕放电与绝缘液体中流注放电的测量和分析(英文)

Insulation is one of the most important parts in a high voltage equipment.There are gaseous,liquid and solid insulations which are commonly used.In a high voltage transformer for example the insulating materials are all used.During operation of a high voltage equipment high electric stress may occur.Under extreme condition failure of the insulation may take place.Excessive electric field in air may cause corona discharges while in liquid insulation discharges may take place in the form of streamer.This paper reports experimental results on the corona and streamer discharges in air and silicone oil.The discharges were artificially generated around a needle tip in a needle-plane electrode system with gap length of 4 mm under sinusoidal and triangular voltages.The needle was made of steel with tip radius of 3 μm and curvature angle of 30°.The needle was made by Ogura Jewelry.The discharge pulses were measured using personal-computer based partial discharge(PD)measurement system with sensitivity of better than 0.5 pC.The system is able to measure discharge in time sequential.Phase-resolved analysis of the discharges was done to interpret the physical processes behind the discharges.The experimental results showed that corona discharges took place at negative half cycles.The discharges were concentrated around 270° of phase angle of applied voltage.The discharge magnitude and discharge number of corona clearly dependent on the instantaneous of applied voltage.These were strongly supported by the application of triangular voltage.Streamer discharges occurred at both positive and negative half cycles.The discharges pulses concentrated around the peak of applied voltage at phase angle of 90° and 270°.Experimental results under sinusoidal and triangular voltages revealed that streamer discharge magnitude as well as probability of occurrence was strongly dependent on the instantaneous applied voltage.     

等离子体子弹环形结构的形成机制(英文)

The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma dynamics module.The obtained radial distributions of the electron’s number density and the nitrogen’s metastable number density have different structures under different types of reactions or air contents in the model.It shows that total electron impact ionization plays an important role in sustaining the discharge,and together with Penning process,they lead to the shifted-off structure of electron number density.Meanwhile,the ring structure of plasma bullets forms mainly due to the excitation reaction of nitrogen molecule on air contents.     

高压下非均匀电场中局放机理的建模(英文)

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.     

大气压下重复频率纳秒脉冲气体放电中X射线的辐射特性(英文)

Pulsed discharges can generate high power densities and high equivalent electric fields in plasma to emit X-rays,which is closely related to discharge mechanism.In this paper,discharge characteristics and X-ray emission of typical nanosecond-pulse discharges(corona,diffuse,spark or arc)are reviewed.Especially,the diffuse discharges are observed at pulse repetition frequencies up to 1 kHz.Factors influencing the discharge characteristics and X-ray emission are analyzed,such as the gap spacing,parameters of the applied pulse(amplitude,pulse repetition frequency),anode and cathode materials,and curvature radius of cathode.It is concluded that the maximum X-ray intensity is obtained in a diffuse discharge,and the X-ray intensity is affected by the pulse repetition frequency,applied voltage,anode material,and curvature radius of cathode.For example,X-ray intensity increases with the pulse repetition frequency and the atomic numbers of the anode material,but it decrease with the increase of curvature radius.It is also shown that the cathode material has no obvious influence on the X-ray intensity.