低气压氮气中放电形式转化的研究

目前广泛采用介质阻挡放电来获得大面积的均匀放电,但在常压下尤其是在空气中这种放电通常为细丝状放电。为研究在氮气中由均匀放电向柱状放电或丝状放电转化的过渡过程随外加电压变化的规律,实验研究了3.5-20kPa的氮气中,介质阻挡材料分别为聚对苯二甲酸乙二醇酯(PET)和石英的介质阻挡放电现象和电流波形随外加电压的变化情况,研究比较了介质材料对放电现象和特性的影响。研究发现,放电可在低于初始放电电压的情况下维持,并由丝状放电形式向柱状放电形式转化,放电电流和放电面积随之增大。实验结果表明,在低电场下放电会变得更加均匀,可能存在某种由丝状放电向柱状放电过渡的放电形式。但研究未能验证驻极体表面电荷去吸附对放电的影响。     

氖气介质阻挡放电中斑图放电与均匀放电模式的转化

为了找到控制非均匀放电向均匀放电转化的条件,采用楔形气隙研究了氖气介质阻挡放电(DBD)中均匀放电和斑图放电模式之间的转化条件。实验发现,随着气隙距离的增大,放电由斑图放电逐渐向均匀放电过渡。对其放电特性的研究结果表明,在相同的气压和气隙距离下,外加电压的增加将导致均匀放电向斑图放电转变;在相同的外加电压和气隙距离下,气压的升高将导致斑图放电向均匀放电转化。经过分析发现这种转化现象的本质与电场强度E与气压p的比值E/p有关,即在一定的气隙距离下,E/p的增加将导致均匀放电向斑图放电转变。实验结果对空气大气压均匀辉光放电的产生具有一定的参考价值。     

大气压氦气介质阻挡放电的二维演化过程

为了研究大气压氦气的介质阻挡放电机理,利用像增强高速相机(ICCD),以20ns曝光时间,拍摄了多组时序发展的时空分辨放电图像,揭示了放电形式由汤森放电向辉光放电的演化。所测阴极位降区厚度0.4mm,应属亚辉光放电类型,而底面拍摄的图像则揭示了放电径向发展的过程。将放电图像转化为可视性更强的三维图像后,发现放电由覆盖整个电极的微弱汤森放电起始,在场强略高的中心处率先发展,并迅速向外扩散。     

大气压氦气介质阻挡多脉冲辉光放电的光学演化过程

为研究大气压介质阻挡多脉冲辉光放电的模式转化规律及其放电机理,在6mm氦气中进行了3脉冲辉光放电试验,测量了相应的电气参数,并利用增强型电子耦合器件(intensified charge-coupled device,ICCD)拍摄了放电间隙侧面的短时曝光图像,提取放电图像的灰度值并绘制出光强在气隙间的分布曲线,按放电图像特征将放电分成不同阶段,系统研究了各个阶段的放电模式及其转化规律,并探讨了放电的机理。结果表明:放电起始阶段具有汤森放电的阳极发光结构;空间电荷的作用使得放电从开始的汤森放电转化为具有完整的正柱区、法拉第暗区和负辉区的辉光放电;放电电流脉冲之间微弱的发光特性仍具有辉光放电结构,有力证明了放电并未熄灭,而是维持着较弱的辉光放电。     

水中脉冲放电活性粒子的研究

通过发射光谱和化学方法检测蒸馏水中脉冲放电产生的活性粒子，研究了氧气流量造成的放电形式变化(流注和火花放电)，活性粒子(包括羟基、激发态氢原子、氧原子和过氧化氢)变化。实验表明放电形式对各种活性粒子的产率有明显的影响，而气体流量的大小直接决定放电形式的转变，其中氢原子发射光谱强度的变化可以直接表示这种转变，这种转变也决定了OH和H发射光谱强度的差异。     

Influences of gas density depletion on high‐pressure,pulsed‐glow discharge

High‐pressure, pulsed glow discharge has been studied for the excitation discharge in TEA gas lasers. Various instabilities occur in the subsequent discharge, which induce the arc and collapse for the highly repetitive operation. In this paper, the influences of the gas density depletion on the high‐pressure, pulsed glow discharge have been investigated, eliminating the other instabilities such as shock waves, residual ions, discharge products, and electrode heating. The gas density depletion was produced by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurring in the presence of the gas density depletion with that by the double‐pulse experiment in a stable gas. The big gas density nonuniformity tends to cause the arc without the shocks, ions, discharge products, and electrode heating. The transition from glow to arc discharge discontinuously occurs with respect to the gas density depletion. On the other hand, the second discharge in the double‐pulse experiment becomes an arc in much smaller gas density nonuniformity, and the transition from glow to arc occurs gradually. The arc discharge might be driven by some factors other than the gas density depletion. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 9–16, 2000     

常压单极性纳秒脉冲DBD模式的实验研究

介质阻挡放电(DBD)是产生低温等离子体的重要方法。实验研究的DBD由上升沿15 ns,半高宽约30ns最高重复频率1 kHz的正极性纳秒脉冲产生,测量了DBD电压、电流以及放电图像。结果表明,空气间隙上发生两次放电,分别发生在施加电压的上升沿和下降沿末端,电流峰值可达百安培量级,峰值功率可以达到MW级。放电图像显示放电分为均匀放电和丝状放电两种模式,且阻挡方式和重复频率都是影响这两种放电模式相互转化的重要因素。     

针-板电极下针尖曲率和铝箔尺寸对放电机理的影响

为研究电力设备中不均匀电场下的气体间隙击穿现象,通过搭建局部放电ns级放电电流测试系统,研究了针-板电极下针尖曲率半径和铝箔尺寸变化对放电特性的影响。在无铝箔覆盖时,随着针尖曲率半径的增大,电流脉冲幅值增大,其上升沿、下降沿和脉宽都减小。正极性放电电流幅值大于负极性放电电流,其电流脉冲上升沿和下降沿都要小于负极性放电,这可以用流注理论很好地进行解释。随着铝箔面积的增大,电流脉冲幅值和上升沿都减小,下降沿和脉宽增大。然而负极性脉冲上升沿在铝箔直径为5mm时出现最小值。当介质表面有铝箔覆盖,针尖曲率较小时,放电情形类似于无铝箔覆盖的情况;而当针尖曲率较大时,负极性脉宽小于正极性脉宽,其电流幅值大于正极性脉冲。由此推测,在针尖曲率较大铝箔覆盖时放电机理发生了改变,产生了不同于流注放电的另一种放电。     

大气压下辉光放电的产生

阐述了产生大气压下辉光放电的几种方法。在直流电场中,通过改变阴极的结构,抑制了辉光放电向弧光放电的过渡,从而实现大气压下辉光放电;在交流电场中,利用介质阻挡层和高频激励源,可获得稳定均匀的大气压下辉光放电。     

基于波形参数法的电场畸变对局部放电特性影响分析

通过搭建局部放电纳秒级放电电流测试系统,研究了针-板电极的畸变电场下局部放电的特性,以及针尖曲率半径和铝箔尺寸变化对放电特性的影响。研究表明,不同电场畸变条件下放电存在较大差异。当介质表面无铝箔覆盖时,正极性放电电流幅值大于负极性放电电流,其电流脉冲上升沿和下降沿都要小于负极性放电,这可以用流注理论很好的进行解释。当介质表面有铝箔覆盖,针尖曲率较小时,放电情形类似于无铝箔覆盖的情况;而当针尖曲率较大时,负极性脉宽小于正极性脉宽,其电流幅值大于正极性脉冲。由此推测,在针尖曲率较大铝箔覆盖时放电机理发生了改变,产生了不同于流注放电的另一种放电。本文的研究为波形参数法区分不同放电类型打下了基础。     

空气式静电放电抗扰度试验方法

静电放电(electrostatic discharge,ESD)抗扰度试验作为电磁兼容(EMC)试验的一项重要内容,其执行标准IEC 61000-4-2还存在诸多问题,尤其是空气式ESD的重复性问题。为此,基于动能-势能转换原理,采用导轨带动电极运动结构和步进电机装置,用近似单摆结构的试验方法,设计和研制了2种新的ESD抗扰度试验平台,实现了空气式ESD抗扰度试验中对放电电极接近速度的准确控制。利用这2种ESD抗扰度试验平台对空气式ESD的重复性进行了研究。试验结果表明,ESD参数如放电电流峰值、接近速度和放电电压具有很好的规律性,并且在一定的放电电压和接近速度下,空气式ESD也可以具有较好的重复性。在相同放电电压和接近速度下,利用第2种ESD抗扰度试验平台得到的放电电流峰值和上升时间的变异系数均小于利用第1种ESD抗扰度试验平台得到的放电电流峰值和上升时间的变异系数,因此第2种单摆式ESD抗扰度试验平台的重复性要好于第1种ESD抗扰度试验平台的重复性。     

介质阻挡电晕放电去除二氧化硫的研究

工频高压下线管结构反应器可能出现局部电晕放电及气隙中稳定阻挡放电。根据V-qLissajous图形计算了放电功率。随外施电压上升,放电由电晕放电进入稳定阻挡放电,放电电流幅值达数mA,放电功率密度为数百mW·cm-3,去除SO2的能量效率可达30g/(kW·h)。实验表明,稳定阻挡放电时,较高的电压及较大的放电空间可提高能量利用率。     

亚大气压介质阻挡辉光放电的特性研究

亚大气压强下的均匀辉光放电,有可能成为无汞荧光灯。它在材料表面改性、灭菌等领域也有广阔的应用前景。利用水电极在真空玻璃箱内的亚大气压条件下实现了介质阻挡均匀辉光放电。电流波形与放电均匀性没有必然的关系,周期性出现的单电流脉冲无法作为高频下均匀放电的普适性判据。测量了不同气压下氩放电的发射光谱,发现高气压下由于下能级的吸收增加,氩750～850nm的部分谱线强度反而降低。分析了放电照片的灰度均匀性,认为它可以作为判断均匀放电的定量参数。气压越高,越不容易实现均匀放电。气体的均匀放电的气压上限分别是Ar（760 Torr）,Ar-O2（600 Torr）,N2（525 Torr）,N2-O2（375 Torr）,空气（300 Torr）。电负性的O2和H2O会吸附自由电子,将提惯击穿电压,影响放电的均匀性。     

不同参数条件下水中脉冲放电的电学特性研究

在不同的电压和电导率参数条件下分类实验研究了水中脉冲放电的两种方式 (电弧放电和电晕放电 ) ,采集并分析了实验中的电压和电流数据。然后简要讨论了两种放电方式的产生机理 (与电弧方式的热过程机理相比 ,电晕方式的初始机理还很不清楚 )。最后从实验现象、产生机理和应用前景等方面对比分析了两种放电方式。实验发现在大的溶液电导率下水中电晕放电方式的声学效应明显 ,为水下等离子体声源的设计提供了新的思路。     

气体放电对金属平板强化传热作用的研究

文中对比研究了电晕、介质阻挡以及辉光放电对空气-金属之间对流传热系数的影响作用。通过对加热器功率以及铜板电极温度测量，计算获得在自然对流以及电极间发生放电两种情况下对流传热系数。在气体放电强化传热的作用下对流传热系数获得数倍的增加。在直流电晕放电实验中，当均匀的直流辉光放电产生时，空气-金属之间传热速率获得最大幅度的提高。采用介质阻挡放电在提高空气-金属之间传热速率的同时，放电间隙击穿电压发生显著提高，也使放电在实际应用中更易于控制。     

Laser‐induced burst corona and streamer corona for a positive DC nonuniform field gap in N2/NO mixtures

The characteristic of sparkover in a DC nonuniform field gap is closely related to the discharge mode at the onset time of corona. In order to investigate the transition mechanism from burst corona to glow corona or streamer corona, a discharge experiment which is controlled by a pulsed laser in N₂/NO mixture has been performed. From highly sensitive observation of discharge luminescence which corresponds to the discharge current wave, the transition from burst corona to streamer corona is identified by the electron avalanche, which is formed initially at the tip of the rod electrode with the highest electric field, and the effect of secondary ionization. Moreover, it is verified that the measured electron burst drift time with laser irradiation in the discharge gap is determined by the electric field of the discharge gap. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 10–17, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10007     

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.     

空气条件下介质阻挡放电影响因素的研究

为了解决低气压等离子体用于工业生产时存在真空系统昂贵和难以实现试品的批量处理等缺点,采用环氧树脂和聚四氟乙烯(PTFE)作为介质阻挡放电(DBD)的阻挡介质,探讨了在不同放电间距d(2-5 mm)、气压p(10-100 kPa)和外施电压U下的放电特性。结果表明,PTFE为阻挡介质,d≤3 mm时,在大气压下可利用DBD的形式产生辉光放电,当d>4 mm时,则不能得到稳定的DBD;在不同气压下,DBD稳定放电对应的电压区间范围在d为3 mm时最大;次大气压下辉光放电的特征较大气压下更明显,辉光放电更易获得,稳定放电的电压区间也更大。     

Prediction of tree initiation by analysis of discharge magnitude and discharge luminescence at each phase angle section

Partial discharge is one of the causes of deterioration of insulating polymer materials subjected to high voltages. In this case, the deterioration that is caused by partial discharges in gaps, such as voids inside an insulator, is of particular importance. In this study, the prediction of tree initiation due to partial discharge occurring in voids is considered. New tree initiation diagnostic methods are proposed by measuring discharge magnitude and discharge luminescence in each phase angle section of the applied voltage. It is noted that some samples revealed different time dependence of partial discharge patterns even under the same measurement condition. These patterns were the case of occurrence of swarming pulsive micro discharges (SPMDs) before tree initiation and the case of no occurrence of SPMDs. The prediction of tree initiation by using moving average of the discharge magnitude is discussed. We propose the parameters to reflect a pre‐tree initiation mode and also evaluate their usefulness for the prediction of tree initiation by using moving average analysis. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(2): 22–29, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10076     

Numerical investigations of a repetitively pulsed MPD thruster

Performance of a repetitively pulsed self‐field MPD thruster consisting of a flared anode and a short cathode was numerically investigated. For a time‐averaged input power of 100 kW and argon propellant, thrust and thrust efficiency were surveyed for various discharge frequencies under the condition of continuous propellant injection and a constant discharge duty ratio of 0.5. The results suggest that thrust efficiency of repetitively pulsed discharge operation can be improved up to about 16% with increasing discharge frequency owing to a relatively high time‐averaged electromagnetic thrust and an increase in aerodynamic thrust, and can surpass that of continuous discharge operation above 50 kHz. It is also shown that the frozen flow loss can be reduced by increasing discharge frequency, because the input power needed for reionization of the propellant can be suppressed. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.