冲击波压力在分叉管道内的传播规律

为研究冲击波在分叉管道内的压力分布和衰减规律,搭建模块化分叉管道模型,进行冲击波传播试验,得到了不同破膜压力和不同分叉角度条件下冲击波在管道内各测点的超压峰值,并利用兰基涅-胡果尼方程插值拟合衰减曲线。使用FLUENT软件的压强速度关联算法对冲击波在管道分叉处的传播过程进行数值模拟,观察管内压力流场分布。得出结论:分叉角度对干管和支管的压力分布有显著影响,冲击波在管道内的衰减速率与破膜压力有关。30°、90°和150°三种分叉管道中,90°分叉管道支管的平台压力最低。同一破膜压力下,支管与干管的衰减速率变化趋势相反。     

Investigation of a new extinguishing principle for a gas circuit breaker

A self-extinguishing principle of a gas circuit breaker (GCB) without puffer action (autopuffer GCB) using an external magnetic field was investigated to improve the interrupting capability in the small current region (several kA). Properties of the rotating speed of an arc, the arc voltage, and the gas pressure rise in an expansion space under the external magnetic field were studied experimentally. The relation between the interrupting capability and the radial magnetic flux density in the autopuffer GCB with a permanent magnet (magnet-assisted autopuffer GCB) was obtained experimentally and also analyzed numerically. The results are summarized as follows.

• 1 The arc column is driven in the azimuthal direction by the radial component of the external magnetic field.
• 2 The rotating speed of the arc driven by the radial magnetic field of a permanent magnet remains constant in the arc current range below several kA, and it decreases with an increasing current in the current above several kA.
• 3 Since the arc rotation raises the arc voltage and gas pressure in the expansion space, the gas flow from the expansion space to the arc increases in the vicinity of current zero. The interrupting capability is then improved in the small current region.
• 4 It is confirmed that the magnet-assisted auto-puffer GCB has a good interrupting capability not only for the large current region but also for the small current region.

     

高压脉冲直流等离子体电源的研制及其放电特性

为满足高超声速磁流体流动控制实验研究的需要,采用同步高压脉冲电离和直流维持放电技术,研制了一种适用于高超声速激波风洞实验系统的高压脉冲直流等离子体电源。首先进行了静止低气压条件下的放电特性研究。通过高速电荷耦合器件(charge coupled device,CCD)可以发现:初始时刻直流放电强烈,放电电流达到16A;随着电容储存能量的消耗,放电电流逐渐减小,放电强度缓慢减弱,直至完全消失,放电形状近似为一圆形。然后进行了高超声速气流中无磁场激励、磁流体(magnetohydrodynamics,MHD)逆气流减速激励和MHD顺气流加速激励条件下的放电特性研究,提出了用于高超声速激波风洞实验系统的MHD激励强度判定标准。研究结果表明:高超声速气流中施加磁场能够起到稳弧的作用,有磁场激励条件下的电源能量消耗约是无磁场激励条件下的3～4倍;MHD加速激励同MHD减速激励的功率相等,而MHD加速激励的电源能量消耗高于MHD减速激励的电源能量消耗。     

X箍缩放电等离子体及其应用

为了拓展读者对高电压新技术及放电等离子体的视野,根据作者近期的实验结果,并结合一些他人的研究成果,对X箍缩放电等离子体及其应用进行了综述。X箍缩是以两根金属细丝作为脉冲大电流的放电负载,由于脉冲大电流磁场对等离子体的箍缩作用,在叉丝交点处将产生高温度高密度等离子体,并形成高亮度的亚ns脉冲X射线μm级点源。鉴于这两根细丝交叉并接触于一点呈"X"形状,故称之为X箍缩。X箍缩可以作为X射线源,应用于高能量密度物理领域,例如对丝阵负载Z箍缩等离子体进行背光照相,也可以应用于生物医学领域,例如对X射线弱吸收的生物体进行相衬照相。文中首先简单介绍了X箍缩工作原理及其放电发展过程;然后描述了X箍缩装置构成、驱动电流参数及其和叉丝负载质量的匹配要求;紧接着重点并详细介绍了X箍缩的X射线辐射特性;最后给出了X箍缩在X射线背光照相和相衬成像方面应用实例。     

基于LabVIEW和文丘里管的气体流速检测仪

针对家用燃气热水器排烟气流速流量实时检测的需求,研究了基于文丘里效应的检测装置,设计了与燃气热水器排烟管相连接的文丘里管结构,开发了基于虚拟仪器平台LabVIEW的检测系统,应用硅膜片微差压式传感器检测文丘里管输出的差压信号,并对差压信号进行了标定实验,通过与数字风速风量仪进行检测对比试验,证明了检测装置的精度能达到应用要求,为未来在家用燃具、厨具等产品上研发低成本、高精度的气体流速流量实时检测装置奠定了基础。     

用响应曲面法研究高梯度磁场下燃煤PM10的捕集效率

建立高梯度磁场捕集燃煤PM10实验台,采用电气低压冲击器测量颗粒浓度的变化,利用响应曲面法对PM10捕集效率进行实验研究,得到捕集效率的预测模型。计算结果表明通过该预测模型可以很好地描述捕集效率与颗粒浓度、磁场强度、气体流速和磁介质填充率等重要操作参数之间的关系。因素分析表明磁场强度对捕集效率的影响最大,同时颗粒浓度与磁场强度、磁场强度与气体流速以及磁场强度与磁介质填充率的交互作用均对捕集效率有重要的影响。     

Transient phenomena of disk MHD generator due to change of load resistance

The results of an experimental study on transient phenomena in a closed cycle disk MHD generator are described in this paper. The transient phenomena were caused by a steplike change of load resistance during testing of the shock‐tube driven disk MHD generator. The load resistance was varied by using an IGBT (insulated gate bipolar transistor) installed in the load circuit. When the load resistance was changed from 0.096 Ω to 2.5 Ω, overshoot of the Hall output voltage and of the Hall electric field was observed, and a large fluctuation of static pressure was also observed. At the same time, a spikelike increase of the cesium recombination continuum and line spectrum appeared just after the load change. The results of quasi‐one‐ dimensional numerical simulation indicate that the observed overshoot was caused by the following phenomena: (1) a steep reduction of the Hall current and a steep increase in both the Faraday current and the electrical conductivity and (2) a slow reduction of the gas velocity due to the enhanced retarding force. Furthermore, the measured spikelike increase of the radiation intensity was ascribed to an increase of electron temperature and electron number density due to a steep increase of Joule heating. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 34–42, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21004     

用镜像法计算大型电力变压器漏磁场的研究

大型电力变压器漏电抗及电磁力的计算实际上就是变压器漏磁场的计算,采用镜像电流法对变压器铁心窗中的漏磁场进行了计算,给出了场点处磁感应强度与最高镜像电流次数奇偶性的关系,用最高镜像次数相邻的镜像电流及实际电流算得的场点处磁感应强度的平均值近似场点处磁场感应强度的实际值。用此方法计算变压器的漏磁场,在编程及计算工作量相对较小的情况下,可获得具有很高精度的磁感应强度。     

黎开管自激热声不稳定的数值模拟

为探索燃烧过程中热声不稳定的产生及控制机理，采用计算流体力学(CFD)的方法，模拟了黎开(Rijke)管内的自激热声不稳定，得到了管内压力、速度、温度和气体密度的起振，最后达到极限周期的过程。通过压力与速度的相位分析，验证了瑞利准则(Rayleigh criterion)是维持Rijke管自激热声不稳定的关键因素；同时，模拟结果给出了Rijke管内的振荡流场和振荡温度场，实现了热声不稳定的可视化。通过与前人的试验研究相比发现，模拟值与试验数据基本一致，说明CFD是研究Rijke管自激热声不稳定的有力工具。     

变电站接地网腐蚀诊断磁场检测系统的设计与应用

对变电站电磁环境测量和接地网进行仿真计算,设计和开发了变电站接地网导体腐蚀诊断的磁场检测系统.通过对接地网的两个上引导体注入异频正弦波激励电流,探测激励电流在地表面上产生的磁感应强度分布,实现了变电站接地网导体的腐蚀状态和断点故障的诊断.现场测试表明,该系统的抗干扰能力、分辨率和测量精度均能满足诊断需要,诊断方法可行,测量系统可靠,提高了诊断的效率.     

Development of a high‐pressure air‐insulated 72/84‐kV disconnecting switch corresponding to bus‐transfer current switching

SF₆ gas has excellent dielectric strength and current interruption performance. For these reasons, it has been widely used for gas‐insulated switchgear (GIS). Today, such global environmental problems as global warming are important issues of concern. SF₆ gas is known as a greenhouse gas with a long atmospheric lifetime, and has global warming potential of 23,900. SF₆‐free 72‐kV GIS was recently developed by using high‐pressure air and a gas/solid hybrid structure. But an alternating current disconnecting switch (DS) has yet to be developed thus making this type of SF₆‐free 72‐kV GIS unsuitable for double bus‐bar application. Consequently, the development of a high‐pressure air‐insulated DS corresponding to bus‐transfer current switching has been expected. The bus‐transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS, efforts must be made to reduce arcing damage to the electrode. This paper describes the fundamental characteristics of current interruption in the plain break type and the magnetic field driven type. Then, average arcing time of the magnetic field driven type was estimated by magnetic flux density. Finally, two types of DS, which were a high‐speed plain break and a low‐speed magnetic field driven, were confirmed to comply with bus‐transfer current switching requirements on JEC standard. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 48–55, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20595     

弧线管微粒污垢特性的实验研究

微粒污垢的沉积造成换热面流动阻力增大，传热效率降低，腐蚀加剧。文中通过不同流速和微粒浓度下微粒污垢的加速实验，得到了弧线管微粒污垢渐近热阻值和诱导期；同时，用数值方法模拟了弧线管的内部流场和壁面剪切力。结果表明：弧线管微粒污垢的渐近热阻值和诱导期与微粒浓度和流速有关，流速增大、微粒浓度降低，其诱导期延长，渐近污垢热阻减小。而且，在清洁状态、析晶污垢和微粒污垢状态下，弧线管比对应光管都具有良好的传热和阻垢性能，其主要原因是由于弧线管内部流场和壁面剪切力周期性变化所引起的。     

Stabilization for thermomagnetic instability of CuNi/NbTi superconducting wire in spatially distributed magnetic field

Thermomagnetic instability in superconducting wires composing multistrand cables is a problem in the development of cables with large current capacity. This paper elucidates the quenching properties of ac superconducting wires in a distributed magnetic field applied to the strands in the cable, and the stabilization of the ac superconducting wires considering the effect of the longitudinal magnetic field or the fraction of copper embedded in each strand. First, the degradation of the quench current of CuNi/NbTi superconducting wires in a distributed magnetic field is exhibited with simple test samples. Second, the quench properties of the strand in a (6 + 1)³ cable and the optimal twist pitch of the cable for high stabilization are discussed. Last, the effect of copper on the quench properties of the strand and the appropriate fraction of copper for suppression of quench current degradation in a distributed magnetic field are discussed. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 26–34, 2001     

特高压交直流并行输电线路混合电场分布

为了降低交直流并行线路混合电场在输电走廊附近民房及金属支架上产生的静电感应影响,在交直流线路并行区域民房平台上搭建平行于线路的屏蔽线,分别测量了平行线路方向的工频电场和直流合成场分布,分析了屏蔽线架设高度、根数等对线路混合电场的屏蔽效果。在并行区域地面搭建了葡萄架模型,测量了不同网架结构的感应电压分布。结果表明,架设屏蔽线能够有效改善导线下方空间混合电场且存在最佳屏蔽方式,葡萄架感应电压受架设方式和长度的影响较大,最大感应电压对人体无电击刺痛感。     

Streaming electrification of thin insulating pipes under electricfield

Streaming electrification under dc and ac electric fields was investigated by using test pipes and oil circulation apparatus. We used two different test pipes, one made of pressboard, and the other of insulating paper. At first, the amount of static charges which flowed into the test pipes was measured without electric field. For the experiment using an insulating paper pipe, when the oil temperature increased, the measured current curve shows a peak. When the velocity increased, the current increased proportionally from the 2nd to 4th power of velocity. For the experiment using a pressboard pipe, the current increased proportionally from the 3rd to 5th power of temperature, and by the 1st power of velocity. Then, we applied ac and dc electric fields on the test pipes and the current from a relaxation tank to ground was measured. The ions in oil carry the charges, so an electric field affects ions in the oil. It makes the mathematical approach to streaming electrification difficult. We know that as the electric field intensity increased, the current due to selective adsorption of the test pipe was increased. The current vs. velocity curve under ac electric field had a peak point in velocity     

Discharge Mechanisms in Neutral Gas Lasers

The equations which govern the discharge phenomena in neutral gas lasers are cast into simplified form which brings out the dependence of laser properties on the external parameters of importance?gas pressure, tube diameter, and tube current. The well known empirical scaling laws which govern neutral gas laser operation follow quite naturally from this procedure. Specific examples are given to illustrate agreement with experiment.     

The effect of an externally applied radio‐frequency electromagnetic field on the performance of a disk MHD generator

The effects of an externally applied radio‐frequency (rf) electromagnetic field on the nonequilibrium performance of a disk MHD generator were examined experimentally. As a preliminary experiment, plasma production by the applied rf electromagnetic field was attempted in the disk generator (Disk‐PIA), in which rf induction coils were embedded in the one‐side disk wall, under the conditions of no seeding, no flow, and no magnetic field. From the results of the preliminary experiment, it was confirmed that the argon plasma (～110 Torr) was produced uniformly in the azimuthal direction by the rf electromagnetic field even in the presence of exposed anodes in the faced disk wall and metallic support at the disk center. In MHD power generation experiments with the Disk‐PIA installed in the shock‐tube facility, the increase in the electrical output and more indiscrete discharge attributed to the rf electromagnetic field were verified with good reproducibility for the first time. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(4): 46–53, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10009     

特高压直流输电线路离子流场的有限元-积分法计算

针对特高压直流输电线的地面电场和离子流密度的计算问题,采用有限元-积分方法,对双极离子流场的控制方程进行求解,同时还对空间电荷密度初值进行了改进。通过计算,发现该方法能较快地获得稳定的数值解。通过采用该方法对±400kV的直流线路进行了比对计算,验证了该算法的有效性。将该方法应用于实际的±800kV直流输电线路,对地面合成电场和离子流密度进行了计算,分析了导线对地高度、极间距、正负极起晕情况不同以及避雷线对地面合成电场和离子流密度的影响。结果显示随导线高度升高和极间距减小,地面的最大电场强度和离子流密度随之减小。在正、负极起晕不同时,负极导线下面的合成电场和离子流密度的最大值比正极大。计算中,考虑避雷线会增大地面的合成场强和离子流密度,但是不明显。     

A method of simulating magnetically driven arcs [in switchgear]

This paper presents a new, practical method of simulating the behavior of arcs driven by magnetic forces in a gas. This simulation method is very useful in designing electric devices using magnetically driven arc techniques. First, the authors describe the arc model. In this model, the arc is assumed to be a chain of small rigid cylindrical current elements. Each element receives Lorentz's force from the magnetic field and a fluid drag force from the surrounding gas. Owing to the similarity between an arc and a rigid column, the drag force of the arc is expressed by that of the column. The element moves with the velocity determined by these forces. Consequently, one can obtain the behavior and the shape of the whole arc. Finally, a simulation example is shown     

压气式气吹灭弧室的气动计算

本文主要计算了气吹断路器中喷口内一维非定常气流流动参数分布。在上游压气室气压变化条件下计算了喷口内气流流动速度和压力分布特性。从理论上分析计算了空载及开断电流为４０ｋＡ条件下电弧热效应对分闸速度及喷口内焓流特性的影响。