电极参数影响射流喷雾荷电量的试验研究

为研究环形电极直径及其相对于喷头的布置方式对雾滴荷电效果的影响,在TR80-02C圆锥雾喷头上,采用5种不同直径的环形电极和5种安装位置进行全因素射流荷电喷雾试验,用网状目标法测量群体雾滴的荷电电流、总质量和试验时间,用荷质比来评价雾滴的感应荷电性能。详细分析荷电电压、电极环直径和安装位置对雾滴荷质比的影响,并在理论上对其显示的特性和机理给出科学的解析。试验结果表明:荷电量随作用于电极上的荷电电压提高而增大;电极环直径增大,雾滴的荷电量反而减小;电极安装位置沿喷射方向前移,其雾滴荷电量增大;荷电量与电极环直径和安装位置间存在线性关系。通过进一步分析,构建了荷电系数与电极参数和位置关系的经验公式,该公式可用于计算和预测感应电极荷电量,为电极参数与静电喷头的合理设计提供科学依据。     

高压脉冲负电晕荷电喷雾试验研究

为减少化学农药带来的污染,采用了荷电喷雾新技术。首先对负高压脉冲电晕荷电机理进行了理论分析,再用网状目标法通过调节电压、极距、电极直径、电极数目等参数进行电晕荷电试验,比较各因素对电晕放电伏-安特性影响及荷电后雾化效果;测量不同电压下雾滴的索太尔直径;并用高速摄影拍摄雾滴带电射流破碎时的状态,得到射流破碎时的雾滴形状。理论分析和试验结果表明,电压越高,雾滴谱较窄,雾滴粒径变细,均匀度越高;揭示了不同影响因素下的雾滴荷电特性,为负高压脉冲电晕荷电喷雾技术的应用和设计提供了理论基础和试验数据。     

湿法烟气脱硫装置和静电除尘器联合脱除烟气中汞的试验研究

采用国际上通用的安大略方法(Ontario hydro method,OHM)对某燃煤电站静电除尘器(electrostatic precipitator,ESP)和湿法烟气脱硫装置(wet flue gas desulphurization,WFGD)前、后的烟气进行采样,应用美国环境总署(enviroment protection agency,EPA)标准方法测定了烟气中Hg0、Hg2+和HgP的浓度,应用全自动汞分析仪DMA80测定固体样品(煤、底灰、ESP飞灰、脱硫产物)中的汞浓度。由汞平衡得出各个环节中的汞所占的份额,分析了ESP和WFGD对烟气中汞的脱除性能。实验结果表明：此燃煤电站烟气中的汞主要以Hg0形态存在,所占份额均大于80%,Hg2+的份额小于20%,ESP可以有效脱除HgP且部分Hg0被氧化为Hg2+。WFGD装置对总汞的脱除率和Hg2+的吸附率均为零,研究发现烟气中大于50%的Hg2+经过WFGD装置后被还原为Hg0。电厂底渣和飞灰中汞的富集因子均小于1,脱硫产物中汞的富集因子均大于1,表明在此电厂中汞在底渣和飞灰中是耗尽的,在脱硫产物中是富集的。     

电极材料对低密度聚乙烯中空间电荷的影响

用电声脉冲法(PEA)测量了不同电极材料对低密度聚乙烯(LDPE)中空间电荷的影响。电极材料为常见的金属,如:铝、含铅黄铜、含锌黄铜和紫铜。实验发现不同电极材料均有空穴和电子注入;并且在实验条件下电极功函数越高越容易注入空穴,功函数越低越容易注入电子;铝(+)/紫铜(-)电极系统能有效减少聚乙烯中的空间电荷注入,进而抑制因空间电荷聚集引起的局部场强过高。     

Static Probe for Electrostatic Field Measurement in the Presence of Space Charge

The conduction current to a probe incorporated into an electrode is proportional to the strength of the charge-carrier drift field; this current is modulated by a bias voltage applied betwen the probe and the electrode. The current/bias-voltage probe characteristics are described which have been derived from computation of the bias field distribution. From these design data the probe can be used to determine the strength of an unknown carrier drift field; an inherent self-verification capability is a feature of the technique. Examples of applications to direct-current point-plane corona are given.     

电极材料表面改性对交联聚乙烯内空间电荷注入的影响

使用溅射镀膜法在纯铜片上溅射金属Mo,将表面改性后的铜片作为电极,利用电声脉冲法(PEA)测试不同溅射电压制备的铜片作电极时交联聚乙烯(XLPE)内的空间电荷分布情况。结果表明:随着制备铜片电极时溅射电压的增加,注入XLPE内的空间电荷量减少,溅射电压为440V时,XLPE内部几乎没有空间电荷积聚。将PEA测试后的XLPE试样进行热刺激电流(TSC)分析,发现镀Mo后,随着溅射电压的升高,被陷阱捕获的空间电荷量逐渐减小。     

导电碳黑填充EVA半导电电极对聚乙烯中空间电荷注入的影响

为探索导电碳黑填充EVA半导电电极对聚乙烯中空间电荷注入的影响,分别将碳黑以3种不同的比例填充到EVA中作为聚乙烯的电极,碳黑的体积分数分别为27％,32％和34％。高压下,采用压力波法研究聚乙烯中空间电荷的注人情况,并对测量结果进行定性的比较和分析。结果表明,聚乙烯样品中空间电荷的注入量随着电极中碳黑填充率的增大,空间电荷的注入量反而减小。这与理论预测相符,电极中碳黑的填充率越大,与聚合物接触的界面处碳黑颗粒的排列就越密集,颗粒表面最高场强就越低,且表面局部高场区在平均场强的延伸范围就越小,从而就减少了空间电荷的注入。     

低密度聚乙烯空间电荷与电导电流的联合测量

聚乙烯非常容易积累空间电荷,造成聚乙烯绝缘电缆用于高压直流输电时容易出现绝缘劣化和使用寿命减少的问题。为了研究绝缘材料在直流电场下的空间电荷特性与电导特性,考虑到由于外电流存在位移电流分量,对于同一块试样分别测量得到的结果并不能进行严格的联合分析,基于脉冲电声法（pulse electro acoustic, PEA）原理设计了一套能够对平板试样进行“同区分时”测量空间电荷和外电流的实验装置,联合测量了低密度聚乙烯（low density polyethylene, LDPE）在室温下的空间电荷和高场电导。实验结果表明：随着施加场强的升高,阳极异极性空间电荷逐渐增加,阴极由同极性注入转变为异极性空间电荷积累,这与材料内部的杂质解离以及不同电极材料的选取有关。低电场条件下位移电流在外电流中所占的比例大于电导电流,传导电流密度与电场强度的关系也符合空间电荷限制电流（space charge limited current）理论。     

Bi-Ionized Space Charges Generated by Means of Corona

Due to the extensive usage of unipolar corona in electrostatic precipitators, electrostatic painting, mineral ore separation, and other applications, most of the past studies of particle charging and electric fields in space-charge regions have focused on the unipolar corona. As such, while the basic equations for particle charging in bi-ionized fields are known, relatively little experimental work may be found in the literature. A test chamber and a wire probe assembly have been constructed allowing the investigation of electric fields in the bi-ionized space between parallel wire coronas for various gas mixtures, pressures, and spacings. Results are presented for experiments in air, CO2, and CO2-nitrogen mixtures, and they seem to indicate that a substantial amount of recombination of positive and negative ions occurs. The resulting average electric field intensity over a large section of the bi-ionized space between the corona wires was found to be uniform.     

交、直流电场作用下交联聚乙烯中的空间电荷习性

Polyethylene is one of the widely studied polymeric insulation materials,which have been used extensively for cable insulation.One of the major issues related to polymeric materials is its easy formation of space charge,a high chance to cause electric field distortions.This phenomenon is more significant under high voltage direct current(HVDC)stresses.Space charge can also be observed under high voltage alternative current(HVAC)stresses but with much less intensity due to the limited charge injection period and the effect of charge recombination caused by the constantly variance of the external fields.When considering the situation of an AC voltage combined with a DC offset,a possible scenario in HVDC technology,there was little research on charge dynamics in the insulation in terms of both experimental and simulation work.In this paper,a numerical simulation based a bipolar charge injection/transport model is used to obtain characteristics of space charge in polyethylene under the combined AC and DC high voltage at room temperature.The bipolar charge injection/transport model,which is widely used in HVDC space charge simulation,is applied in the combined conditions.The overall applied voltage,consisted of root mean square(RMS)values of the AC voltage and DC voltage,is kept the same,while the DC component’s voltage ratio and AC component’s frequency are changed respectively,to illustrate their effects on the space charge dynamics within the insulation under combined electric fields.The simulated charge distributions present notable differences when DC offset is increasingly added in,while relatively small differences when AC component’s frequency altering,especially for the cases whose frequency exceeding 0.5 Hz.     

Experimental Investigation of Impulse Characteristics of Practical Ground Electrode Systems

In this work, the results of an experimental study of the impulse characteristic of practical ground electrodes consisting of horizontal conductors of various lengths and full-scale tower footings were...     

Computational Study of Cymatics with Experimental Analysis

Cymatics is a visual representation of sound and vibrations, on surfaces of plates, diaphragms, and membranes in the forms of auditory-images. The surfaces that are exposed to these vibrations are sprinkled with fine particles that ac-cumulate at nodes, to create visualizations of specific geometry unique to the particular frequency. This paper dis-cusses the designing of an experimental platform, dedicated towards observing the behavior of cymatics, through analysis of such visualizations (Chladni patterns). This is further investigated by performing a numerical modelling using finite element simulation. Two millimeter thickness Aluminum (Al) plates of three shapes consisting of sur-faces with equal areas were used for both experimental and finite element analysis (FEA). FEA was performed using ANSYS simulation software and patterns were derived for different vibrational frequencies. The results demon-strated that the 60% of the experimental imagery conforms with the visualization generated by ANSYS software. Additionally, the lowest average frequency differences with respect to the simulation results an average deviation for similar images was found to be 9.2% and 2.8mm for the triangular shape plate, validating that the shape of the plate plays a paramount role in cymatics analysis. An image processing technique was used to determine the deviation between the images created by experimental platform and FEA for all the three shapes. The results demonstrate that Chladni patterns are best represented by a triangular shaped plate.     

Numerical and Experimental Study of a Continuous Electrostatic Smoking Process

The smoking process is a batch one with long duration processing (some hours). Deposition of smoke particles can be enhanced by electrostatic precipitation. However, a better knowledge of the fundamental physics is needed to optimize the process. We carried out experimental and numerical studies to obtain essential information on the smoke flow. First, experiments physically characterized the wood smoke. These measures lead us to study the turbulent two-phase flow using an algebraic slip model. The main coupling with electrical forces is taken into account through the slip velocity. Various assumptions were tested concerning the coupled phenomena in order to build an algorithm that is able to simulate these phenomena. Numerical resolutions are compared with data from the literature on a simple electrostatic precipitator (three wires between two plates). Simultaneously, experiments were performed on a simplified scaled-down model of the smoking process (wires and one plate). The results of particle image velocimetry show clearly that the electrostatic precipitation phenomenon is effective above a threshold voltage and is significantly influenced by geometry of electrodes. Experiments and numerical resolutions underwent a validation phase. A small-size industrial demonstrator, of which the promising results will not be discussed in this paper, was conceived by exploiting the presented works.      

多个特高压直流系统共用接地极的研究

根据向家坝－南汇±800 kV直流输电工程的具体参数,利用电磁暂态计算软件EMTP-RV对3个特高压直流输电系统送端及受端分别采用共用接地极方案进行详细的仿真研究,从系统稳态运行角度进行了深入透彻地分析,对该方案的优缺点进行了详细总结,并对该方案下各直流输电控制系统的协调控制提出了可行性建议。仿真结果表明,多个直流共用接地极的方案是可行的,但应该限制接地极接地电阻和引线电阻在一定范围,另外对接地极址的选择和共用接地极本体设计也有较高要求。     

双流体雾化荷电特性试验

为了有效改善石灰浆喷雾烟气脱硫中的浆液雾化,提高烟气脱硫效率,在引入双流体静电喷雾技术中,建立了环形电极的感应荷电的数学模型,计算了电极诱导的电位;采用目标网状法设计了雾滴荷质比Aq的测定装置,测量了不同浆液质量分数w(slurry)、气体流量Qg、液体流量Ql、荷电电压Uq下雾滴的Aq。结果表明,Aq随着Uq的增大而增加;在同一Uq下,Ql增大则Aq变小,Qg增加则Aq增大。随着w(slurry)的增大,Aq呈现下降趋势,在w(slurry)>1.0%时,Aq变化不明显。     

固体绝缘材料空间及表面电荷测量方法

积聚电荷的测量对于研究高压绝缘材料介电及绝缘性能方面起着相当重要的作用。近年来,国内外学者对固体绝缘材料内部及表面电荷测量方法进行了大量的研究,并取得了一些有意义的进展。本文对积聚在固体绝缘介质中的空间电荷和表面电荷的测量方法以及需要解决的问题进行综述。     

湿式电除尘器性能的实验研究及工程应用

湿式电除尘器是实现燃煤烟气达标排放最有效的净化装置,对立式金属极板湿式电除尘器进行了研究。通过建立试验平台,试验研究了不同电场风速、喷水压力及喷水量下的湿式电除尘器的伏安特性。此种型式的湿式电除尘器已在宁波中华纸业自备热电厂得到了应用,测试结果表明除尘效率高达86%,出口烟尘排放远低于20mg/m~3,满足了重点地区烟尘特别排放标准。     

换流变压器空间电荷分布及快速释放方法的研究

换流变压器内部油-纸绝缘结构会发生夹层极化,在界面处存在空间电荷,这有可能引起直流电压试验和交流电压试验中发生局部放电.采用经过二次开发的有限元计算方法,对±500 kV换流变压器在外施直流电压耐受试验、极性反转试验、外施交流电压耐受试验和接地过程中的电场分布和空间电荷分布进行了仿真计算,研究了±500 kV换流变压器空间电荷在试验中的释放过程.     

茂金属聚乙烯改性低密度聚乙烯中空间电荷的机理研究

针对高压,超高压直流塑料电缆中存在的空间电荷效应,文中选用与普通低密度聚乙烯(LDPE)化学结构相似的茂金属聚乙烯(MPE)作为成核剂与LDPE共混,用电声脉冲法(PEA)测量了共混物的空间电荷特性,以差示扫描量热法(DSC)研究了共混物的非等温结晶行为,用高阻计测量了共混物的体积电阻率的变化,结合聚合物的结晶和导电理论,讨论了共混物中空间电荷的形成和抑制机理。测试结果表明:1%的MPE与LDPE共混,能有效降低LDPE中空间电荷效应,提高结晶温度,降低体积电阻率。     

空间电荷对硅橡胶憎水性的影响研究

对硅橡胶试样进行短时间(10 min)的直流加压实验后,直接测量其水珠接触角,发现硅橡胶的憎水性迅速下降。用表面润湿处理的方法将表面电荷导走,再次测量,其憎水性又立刻恢复。经长期加压的硅橡胶试样,在同样的表面润湿处理后,憎水性停留在较差的水平,憎水性恢复的速度也比短期实验要慢得多。用电声脉冲法测量硅橡胶中的空间电荷,并将界面电荷峰值的绝对值与经润湿处理后测得的憎水性进行对比,发现两者存在着相互对应的关系。硅橡胶界面电荷峰值绝对值的提高对应着硅橡胶憎水性能的下降。实验证明,空间电荷的大量积聚会导致硅橡胶憎水性一定程度上的破坏和丧失。