大气压介质阻挡丝状放电时空演化数值模拟

通过数值求解二维流体方程，在均匀的初始条件下研究了大气压丝状放电的整体时空演化.通过模拟可以发现，在丝状放电的时空演化过程中，各条放电通道在不同位置相继发生击穿，且放电通道有遍历整个放电空间的趋势.在一定条件下，放电通道还会发生分裂与合并现象，其中放电通道的分裂导致了放电空间中放电通道的增加，而放电通道的合并则提供了一条放电空间中放电通道减少的途径.研究还表明，介质表面电荷是影响丝状放电整体时空演化的关键因素之一. 关键词： 介质阻挡放电 丝状放电 数值模拟 时空演化     

单极性带电粒子浓度测试方法的研究

提出一种新型球形传感器探测仪，在不同风速、不同激励场强以及不同测试点的情况下对大气压下电晕放电形式产生的带电粒子浓度进行了测量，并分析了等离子体的空间分布情况，同时与DLY型空气离子测量仪的测试结果进行比较. 实验结果表明，球形探测仪对带电粒子浓度的测试结果较为理想，同时，设备操作简单，占用空间小，便于局部定点测量，为研究等离子体的空间分布提供了条件. 关键词： 等离子体 带电粒子浓度 强电场电离放电 大气压     

电子回旋共振放电的电离特性PIC/MCC模拟(Ⅱ)——数值模拟与结果讨论

采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法，应用电磁模型，编写了准三维的电子回旋共振(ECR)放电电离过程的模拟程序，得到了ECR放电过程中电子与离子的相空间分布、电磁场分布.通过对这些分布随时间演化的分析，得出ECR加热发生在ω≈ω_c0且垂直于轴向的区域；ECR区域，微波能量几乎全部耦合给电子，获得能量的电子通过与中性粒子的电离碰撞产生了大量的带电粒子；随着放电的进行，大量带电粒子通过频繁的碰撞，分布由各向异性逐渐趋于各向同性. 关键词： 电子回旋共振放电 粒子模拟 蒙特卡罗 电离     

均匀电场SF6短气隙放电过程动态模拟

根据基本物理定律和流体力学,构建均匀电场下SF₆短气隙放电流体模型,运用通量校正传输法(flux-corrected transport)数值分析大气压下4 mm间隙SF₆的放电过程,展现放电空间带电粒子产生、复合、附着、扩散以及光致电离动态过程,获得了放电间隙电场畸变、带电粒子动力学行为和放电通道形成发展历程和时空分布,根据R-M判据求出模型放电过程中电子崩转向流注的时空临界点,印证了光致电离在流注发展阶段的重要作用.     

平台式和斜坡式表面放电辐射源放电特性的比较

 介绍了平台式和斜坡式两种结构的表面放电辐射源，研究了在1.0 μF和1.5 μF储能电容、15~30 kV充电电压等实验条件下两种辐射源的放电特性，并对实验结果进行了比较分析。得到如下结论：对于斜坡式辐射源，增加电极间距可导致放电回路面积增大，因此等效电阻和等效电感也将增加；在相同电压及电容值条件下，斜坡式辐射源的放电电流、平均沉积功率均小于平台式辐射源的相应值，但放电沉积效率略大；电压升高使放电周期、电流达到峰值时间及放电沉积效率呈减小趋势，对于同一种辐射源，使用1.5 μF电容时放电回路参数更加匹配，放电沉积效率得到提高。     

微波阶梯阻抗变换器低气压电晕放电粒子模拟

采用3维粒子软件VORPAL对微波阶梯阻抗变换器中的低气压电晕放电过程进行了粒子模拟,获得了放电过程中带电粒子实空间分布的时间演变图像,分析并解释了其中低气压电晕放电机理和微放机理之间的关系.模拟结果表明:低气压电晕放电的阈值电压随着气压的增长呈现先减小后增加的变化趋势;并且随着气压的增长,微放电作用减弱,低气压电晕放电作用增强.通过对银和铜两种器壁材料放电阈值的比较,获得了两种放电机理之间的临界气压.     

等离子体电极普克尔盒电光开关单脉冲过程数值模拟

采用流体模型对等离子体电极普克尔盒(PEPC)电光开关单脉冲过程进行了数值模拟分析.模型包括带电粒子连续性方程、动量守恒方程、电子平均能量方程及空间电位泊松方程.分别采用隐式指数差分格式，超松弛迭代法(SOR)和经典四阶龙格-库塔法(R-K)对带电粒子连续性方程，泊松方程和电子平均能量方程进行数值求解.模拟分析了PEPC单脉冲过程中的带电粒子浓度、电子温度、空间电场、PEPC的放电电流、晶体两侧电压和开关效率的时间演化特性.模型得出了PEPC中气体放电等离子体的微观物理过程与PEPC宏观参量的关系，对设计 关键词： 等离子体电极普克尔盒 电光开关 数值模拟 气体放电     

平板CO2激光器中α型RF放电的理论研究

由稳态时粒子数和电流连续性主带电粒子的能量平衡方程，建立了α型平板ＲＦ放电等离子体的理论模型，并用数值方法求得射频放电等离子体中粒子数密度、电场、功率密度、激发效率的空间分布，解释了ＲＦ放电的辉纹结构，分析了放电参数对放电特性的影响。     

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采用粒子模拟与蒙特卡罗模型相结合(PIC/MCC)的方法,建立了氮分子气体辉光放电自洽的混合模型,其中带电粒子在电场中的运动及其产生的自洽场由PIC方法的静电模型描述,粒子间的碰撞过程由MC方法描述。模拟了放电过程及带电粒子(e、N2+、N+)在整个放电空间的行为及与之对应的自洽电场和电势的分布,通过计算带电粒子在负辉区的几率分布函数,讨论了带电粒子(e、N2+、N+)在负辉区的行为和分布特征。计算的分子离子密度与实验结果一致。     

蒙特卡罗模拟在辉光放电鞘层离子输运研究中的应用

利用蒙特卡罗方法模拟氩气直流辉光放电鞘层内离子的运动过程.模拟基于离子与中性原子的电荷转移和弹性散射两种主要的散射过程，考虑了碰撞截面与能量相关和不相关两种情况，在弹性散射中采用了势场相互作用模型和刚性球碰撞两种模型.通过模拟得到不同气压和不同放电电压下离子入射阴极的能量分布和角度分布，并对几种模型的模拟结果进行了比较和讨论. 关键词： 辉光放电 等离子体鞘层 蒙特卡罗模拟     

Ignition of a cloud of dry powder using super brush discharges

Ignition of a cloud of dry powder is a major concern in the field of industrial process safety. The different types of discharges are already defined (spark discharges, brush discharges, propagating discharges, cone discharges, corona discharges) such as their ignition properties in a gas or a dust atmosphere. For example, it is known that a classic brush discharge cannot ignite a cloud of dry flammable dust [6,13]. Glor and Schwenzfeuer performed direct ignition tests using brush discharges and defined that even if the energy released by this kind of discharge equaled the one of a spark, the power released by the brush discharge is too low to trigger an ignition.However, some doubts remained for super brush discharges. A brush discharge as a super brush discharge occurs between a charged insulating object and a conductive electrode. The main difference lies in the surface charge density reached on the insulator that is much higher for a super brush discharge than for a brush discharge. A high charge density can be reached for example using pipes of polyethylene individually charged by tribo-charging piled one above another. Such a configuration was evocated by Lüttgens [12] and tested by Larsen [11] who performed direct ignition tests in oxygen enriched atmospheres.This study is relevant with the actual safety problems since pharmaceutical and chemical powders are well known to generate electrostatic charges during their transport or handling and since the same configuration of independent polyethylene fibers can be found in flexible bulk containers that are one of the most common solutions to package this kind of powder.This paper presents the experimental set-up and the results of direct ignition tests performed with a polyethylene wax whose MIE is lower than 1  mJ at ambient conditions. The electric field reached at 1 m and the charge transfer were also registered and are described. Finally, numerical simulations are carried out to define the original surface charge density in order to help to understand the phenomenology of this discharge and its frequency of occurrence in industry.     

大气压空气中重复频率纳秒脉冲气体放电模式研究

利用上升沿100ns、脉宽150ns的单级磁压缩纳秒脉冲电源,通过电压电流测量和放电图像拍摄实验,研究了大气压空气中极不均匀电场结构重复频率纳秒脉冲气体放电的放电模式。结果表明纳秒脉冲气体放电存在三种典型的放电模式:电晕放电、弥散放电和火花放电。施加的脉冲电压幅值对放电模式影响显著,随着电压幅值的增加,放电依次经历电晕、弥散和火花放电。固定电压幅值时,放电可能同时存在两种模式。重复频率加强了放电强度,弥散放电的激发电压随重复频率的增加变化不大,但火花放电的激发电压随着重复频率的增加而降低。因此降低重复频率有利于在较大电压范围获得大气压空气弥散放电。     

Studies of the parameters of a spark discharge between an artificial charged water-aerosol cloud and the ground

The optical and current characteristics of spark discharges between a grounded electrode and a strongly charged artificial water-aerosol cloud are studied experimentally. The spectral characteristics of the discharge current are investigated using wavelet and Fourier analyses. Three main types of discharge with different final stages are revealed and investigated. It is found that the parameters of a discharge in its final stage depend substantially on the discharge trajectory and the depth to which it penetrates into the aerosol cloud. It is shown that the parameters of the most powerful type of discharge (the brightness of the discharge channel, the current growth rate in the final stage, and the penetration depth into the charged aerosol cloud) are close to the discharge parameters in the main stage of natural lightning. It is also shown that such a discharge neutralizes up to 5% of the cloud charge. In contrast to Fourier analysis, wavelet analysis shows that the signal amplitude (i.e., the energy deposition rate in the discharge channel) is maximum at high frequencies for all types of discharge. Of special interest is the most powerful type of discharge, in which the signal amplitude (which is one to two orders of magnitude larger than in other discharges) is maximum at frequencies of several hundred megahertz.     

Corona discharge in electrospraying

The paper presents investigations of current–voltage and light emission characteristics of electrospraying of various liquids in atmospheric air. The spectroscopic measurements have shown that the onset of corona discharge coincides with the onset of electrospraying, with the voltage increasing. The emission intensity in selected spectral lines during electrospraying depends on spraying mode, discharge power and a kind of liquid. In the specific experimental conditions in air, mainly the N₂ second positive system, which is visible as violet faint light, has been recorded. The emission intensity of other gaseous species, which could be product of electrosprayed molecules decomposition or dissociation, was at very low level for the voltages applied, i.e., for glow or onset streamer discharges. From the measured light emission spectra of discharges from capillary nozzle and liquid jet, the dependence of the amplitude of selected spectral lines on capillary-nozzle voltage has been determined and it was found that this relation can be approximated by a third-degree polynomial function. This approximation has been supported by theoretical considerations. The presented results support the hypothesis that faint electrical discharges (glow, onset streamers) usually occur during and are inherent to electrospraying.     

Concentric-ring structures in an atmospheric pressure helium dielectric barrier discharge

This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a two-dimensional diffusion--drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.     

MEVVA放电在材料表面改性上的应用

本文描述了金属蒸发真空弧放电的特点，阴极弧等离子体的形成过程，以及在加热蒸发电离方式相比ＭＥＶＶＡ放电的优越性。文章还叙述了建筑的ＭＥＶＶＡ离子源的实用参数，工作过程及ＭＥＶＶＡ等离子体源在全方位离子注入装置中的应用。     

氩气介质阻挡放电不同放电模式的电学特性研究

采用水电极介质阻挡放电装置，在气压为40kPa的氩气中实现了弥散、流光和斑图三种不同 模式的放电，并对其光电特性进行测量.通过测量测试电容上的电压，从而将气隙电压计算 出来，发现随外加电压增加，放电起始时刻不断提前，放电占空比增加；对应放电时刻，气 隙电压减小、输运电荷突增，使得气隙电压和电量波形都远远偏离正弦.气隙电压与输运电 荷成非线性关系.给出了外加电压零点对应的气隙电压随外加电压峰值的变化关系.讨论了壁 电荷在放电中的作用及对气隙电压和电量波形的影响. 关键词： 介质阻挡放电 气隙电压 自组织斑图 输运电荷     

Characteristics of the discharge of a charged dielectric in low-pressure air

A charged dielectric generates a series of discharges in the surrounding air when the pressure is steadily reduced from near atmospheric to fractions of a torr. The dielectrics here employed were Mylar and Teflon. With positive polarity different discharge regimes were observed as the pressure varied: spark and long streamers at relatively high pressure; diffuse cloud-like discharges below 266 Pa (2 torr). With negative polarity it is difficult to induce a discharge, due to the absence of an electron-emitting surface. Similarities between our results and some of the features of mesospheric and stratospheric discharges are discussed.     

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在超音速风洞中进行了等离子体气动激励改变激波系结构的实验,考察了介质阻挡放电和横向直流放电对于激波系结构的影响。实验结果表明介质阻挡放电所产生的等离子体能够影响流场附面层。采用逆气流DBD放电后,激波强度略有增大;采用顺气流放电后,激波强度略有减弱。相对于介质阻挡放电,横向直流放电对减弱激波强度影响稍大。     

Study of magnetically enhanced corona pre-charger

In this paper, experimental investigations of the discharge characteristics of magnetically enhanced corona discharges, for the purpose of capturing fine aerosol particles, are presented. The discharge mechanism during such a process is analyzed as well. The effects of magnetic enhancement under different magnet flux densities, and in positive- or negative-corona discharges, were experimentally compared. The magnetically enhanced effects in different inter-electrode regions were studied. Experimental results demonstrated that the magnetic field could efficiently increase the concentrations of both the negative ions and the free electrons during negative-corona discharge. The dominant mechanism of magnetic enhancement in a corona discharge involves the Larmor precessions of free electrons which enhance ionization of the gas molecules near the discharge electrode. A convenient configuration for enhancing corona discharge was formed by placing permanent magnets with a local strong magnetic field near the discharge electrode. A magnetically enhanced negative-corona (MNC) pre-charger was assembled in front of an electrostatic enhancement filter. The influence of the MNC pre-charger on the efficiencies of an electrostatic enhancement filter was measured and compared with that of a conventional corona pre-charger. The free-electron-charging mechanism of the MNC pre-charger was preliminarily analyzed. Our results show that the new pre-charging technique is promising for capturing fine aerosol particles in electrostatic enhancement filters or electrostatic precipitators.