共查询到20条相似文献,搜索用时 9 毫秒
1.
本文基于流体动力学理论改进出一种新的棒-板电极负电晕放电混合数值模型, 模型中加入了27种主要碰撞反应, 并考虑了光电离和二次电子发射过程. 对棒-板间距3.3 mm, 施加电压-5.0 kV情况下进行数值计算, 得到负电晕放电的特里切尔脉冲. 重点分析了单个特里切尔脉冲持续过程中5个关键时刻的微观特征量发展规律, 丰富并量化描述了特里切尔脉冲的微观过程, 主要结论如下: 随着放电时间的发展, 电场集中分布区域向阳极移动且幅值变小, 这对电子崩的发展非常不利. 大部分放电区域都是电中性的, 只有在阴极鞘和阳极鞘附近有带正电的等离子体特性, 带负电的离子云随着放电时间的发展缓慢向阳极发散式移动. 整个特里切尔脉冲持续过程中, 阴极鞘内电子密度几乎为0; 特里切尔脉冲前期, 阴极鞘附近电子密度迅速增加至最大值并保持基本不变; 随着放电时间的增加, 放电间隙内电子密度整体增加, 并且向阳极发展. 在特里切尔脉冲后期, 电子的产生主要来自于N2和O2的碰撞电离, 电子的消失则主要由N2+的复合决定, O4+和O2-分别是数量最多的正离子和负离子.
关键词:
负电晕
混合模型
特里切尔脉冲
微观特征量 相似文献
2.
The current waveforms of the first negative corona pulses in a small point-to-plane gap have been measured with a nanosecond
time resolution in N2 + SF6 and CO2 + SF6 mixtures at a pressure 50 kPa for various contents of SF6 as a function of applied gap voltages. The physical mechanism for the pulses in these mixtures with low concentration of
SF6 has been described using the streamer-based theory. The influence of changing admixtures of SF6 in N2 and CO2 has been compared. Differences in the pulse waveforms observed in N2- and CO2-based gas mixtures are explained by differences in the first and second Townsend ionization coefficients.
This work was supported by the Grant Agency VEGA from the Ministry of Education of Slovak Republic under contracts 1/1011/04
and 1/2017/05. 相似文献
3.
A. K. Shuaibov 《Czechoslovak Journal of Physics》1999,49(2):225-232
The results of investigation of the electrical and optical characteristics of a negative corona discharge in the electrode system of the type needle-grid lit in a He/Xe/SF6 mixture under the pressure of 100–300 kPa are presented in this paper. The given medium is working for a pulse-periodic excimer lamp on = 351 nm XeF(B–X). Distributed on the length of a lamp active media a bipolar corona discharge is intended for using in the electric circulation of the XeF-lamp working medium. It is shown that the given discharge is ignited steadily in the He/Xe/SF6 mixture, containing 0, 5kPa SF6 molecules and is characterised by a low power consumption; the current of the discharge is limited to the development of instability by increasing the voltage on the needles; in hot zones of corona discharge SF6 molecules cause the effective population 6s of XeI state. 相似文献
4.
A numerical study of the impact of different model coefficients on the frequency, DC current, and the rise time of the Trichel pulses in a needle-plane negative corona discharge is presented here. The studied coefficients include the coefficients of the ionization and attachment reactions, the mobilities of the three charged species considered in the model (electrons and positive and negative ions), and the coefficient of the secondary emission of electrons. The characteristics of the pulses were also studied using another set of model coefficients which includes an extended number of reactions such as detachment of the electrons from negative ions. 相似文献
5.
《Journal of Electrostatics》2014,72(5):417-421
Current waveforms of the first negative corona pulses have been measured in O2 + H2 mixtures at a pressure range from 27 kPa to 50 kPa. It was observed that the hydrogen admixtures less than 4% do not change significantly the pulse current waveforms. Effects of changing cathode secondary electron emission were studied using a copper cathode coated by CuI and graphite. The results obtained support the theory of the cathode-directed streamer formation during the negative corona pulse rise. 相似文献
6.
《Journal of Electrostatics》2007,65(10-11):625-630
A numerical study of a negative corona discharge in nitrogen in a point-plane gap using a Monte Carlo method is presented. The simulation provides a detailed structure of avalanches, propagation of successive avalanches and ion distribution can be discerned. The development of electron avalanches is due to ionization and photoionization in the high-field region, while the quenching of the avalanches is due to the low electric field near the plane electrode. Also the accumulation of electrons and positive ions are displayed in detail. The space charge field distortion is studied. 相似文献
7.
The pulsed-periodic regime of a negative corona (Trichel pulses) in atmospheric-pressure air, which leads to explosion emission mechanisms (ecton generation) of pointed cathode erosion, is investigated. The jet erosion process at the copper cathode is discovered, and micrometer dendritelike structures formed by erosion products returning to the cathode are detected. 相似文献
8.
《Physics letters. A》1997,228(3):182-186
A bifurcation analysis of the cylindrically symmetric solution obtained in the framework of the steady-state model of the negative corona discharge in air at atmospheric pressure has been carried out. No bifurcations have been found, which indicates that current contraction probably does not occur in the considered model. It follows that the current-free stripes on the corona cathode surface, observed by previous authors in two- and three-dimensional computer simulation and in experiment, are due to the specific discharge geometry rather than current contraction. 相似文献
9.
《Current Applied Physics》2010,10(6):1391-1401
The purpose of this work is to highlight the chemical kinetics in plasma of pure oxygen. A comprehensive model of ozone generation in wire-to-cylinder negative corona discharge is presented. The model combines the physical processes in the discharge with the chemistry of ozone formation. It is based on an extensive reaction scheme including the major electronic and ionic processes. The importance of excited atomic and molecular states is demonstrated. The obtained results show clearly that the surface material affect quite well the ozone decomposition. 相似文献
10.
Electrical and optical characteristics of a positive corona discharge in He/Xe(Kr)/SF6/CCl4 mixtures, which are of interest for the use in multiwavelength excimer radiation sources, are studied in the needle-grid electrode configuration. The length of the discharge, which is usually used to pump repetitive high-pressure multiwavelength radiation sources, is equal to the length of the electrodes of an excimer laser or lamp pumped by a transverse electric discharge. The discharge current-voltage and frequency characteristics, panoramic emission spectra, and the dependences of the relative emission intensity from the halogenides and excited noble gas atoms on the corona discharge current are investigated. The main processes resulting in the production of halogenides, as well as xenon and krypton excited atoms, in the generation regions of a corona discharge are studied. 相似文献
11.
Corona discharge is a self-sustained discharge which appears at electrodes with a small radius curvature in gas insulation. An almost invisible glow occurs just above the inception voltage. Corona phenomenon is mainly used in electro-technological processes to obtain space charge for electrostatic precipitation, separation of different particles, electrostatic liquid or solid coating, neutralization of space charge, etc. All of these processes rely on a strong nonhomogeneous electric field generated by a point – plate electrode system. When the critical value of the applied voltage is reached, the ionization processes near the point electrode start and give rise to the current between two electrodes. If the pointed electrode is positive, it is possible to observe an anomaly of the current – voltage (I-U) characteristic for the point-plate space. It means that while the voltage is raising the current density decreases in a narrow voltage area (2–3 kV). The anomaly was technically named as negative differential conductivity (dI/dU < 0). Unstable current can have a negative influence on electro-technological processes. The anomaly was detected for different shapes and materials of the electrode as well as for various temperatures and distances between electrodes. An oxidation layer, which appears on the metal electrode, also influences the ionization processes near the pointed electrode and causes a decrease of a current. In this paper measuring of the discharge activity in a point – plate electrode system is presented. Ionization of gas atoms and molecules in a high electric field and the following recombination of electrons and positive ions in the corona region can give rise to high-energy photons which produce new electrons in the field of discharge. Corona discharges are detected by DayCor Corona camera which can register UV emission generated by corona in a day light. The experiment was conducted with various shapes of the pointed electrode and distances between the high voltage and the grounded electrode under applied direct voltage with positive and negative polarity. 相似文献
12.
采用放电图像拍摄和放电波形测量两种方法研究了放电激励HF激光工作介质SF6气体的放电特性。实验结果表明:SF6气体放电可以分为主放电、剩余电压维持和电弧放电3个阶段。主放电阶段为均匀体放电,电容储能大部分在此阶段沉积于放电等离子体中;剩余电压维持阶段无明显放电;在电弧放电阶段激光器以电弧形式消耗剩余储能。通过对放电波形的分析,获得剩余电压及主放电阶段能量沉积效率随充电电压的变化规律。随着充电电压提高,剩余电压下降,沉积效率逐渐提高。沉积效率最大值对应于主放电与电弧放电相接的时刻。 相似文献
13.
A. K. Shuaibov 《Journal of Applied Spectroscopy》1998,65(2):211-217
The article contains results of a study of electric and optical characteristics of a negative corona discharge in a “needles-grid”
electrode system in the mixtures He/Xe and He/Xe(Kr)/HCl, which are used in periodic pulsed electric-discharge Xe(6p−5d),
XeCl, and KrCl lasers. The corona discharge was ignited in a multielectrode system whose length is commensurable with the
length of the active medium of the lasers. Voltage-current characteristics, radiation spectra of the discharge plasma, and
the dependences of the radiation intensity of atomic spectral lines and the band λ=308 nm of XeCl (B-X) on parameters of the
corona discharge are studied. For the mixture He/Xe the corona discharge exists as a spatially homogeneous discharge that
is intermediate between corona and glow discharges and is transformed into an anode streamer at higher charge voltages. Collisional
purification of the 6p states of the Xe atom by helium was observed. In the mixture He/Xe/HCl the corona discharge is ignited
in the form of individual generation zones and a dark external region and can be used in electric systems for pumping the
active media of XeCl and KrCl lasers.
Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 294000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 65, No. 2, pp. 205–210, March–April, 1998. 相似文献
14.
《Journal of Electrostatics》2014,72(2):107-119
To study the characteristics of DC negative corona discharge in a wire-cylinder configuration at an ambient temperature range of 350–850 °C, the I–V characteristics and the current composition are analyzed under different conditions. A simple method is proposed to determine the DC corona onset threshold voltage. At high ambient temperatures, in the DC negative corona discharge gap, some electrons are not attached to the electronegative gas molecules and move to the anode tube. Thus, these electrons form an electron current, which may account for most of the total discharging current. The ratio of the electron current to the total discharging current increases with increasing temperature. In a mixture of O2 and N2 and a mixture of CO2 and N2, the ratio of electron current increases with increasing N2 content in the mixtures. The cathode material has little influence on the corona discharge characteristics at high ambient temperatures. 相似文献
15.
The surface deposits of the traces stained with discharges on the brass plate electrode in atmospheric pressure DC negative corona have been analyzed. The surface analysis showed that the major deposits on the traces originate from nitrogen oxide ions NOx? and neutrals NOx, or carbon clusters Cn. The relationship between the plane positions and resulting deposits obtained with the point-to-plane electrodes with arbitrary needle angle to the plane provided the information about the general behavior of negative ions NOx? and neutral species NOx occurring in stationary inhomogeneous electric fields. 相似文献
16.
K. Sekimoto M. Takayama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(3):297-305
The dependence of negative ion formation on the inhomogeneous electric field
strength in atmospheric pressure negative corona discharge with
point-to-plane electrodes has been described. The distribution of negative
ions HO-, NOx
- and COx
- and their abundances on the
plane electrode was obtained with a mass spectrometer. The ion distribution
on the plane was divided into two regions, the center region on the needle
axis and peripheral region occurring the dominant NOx
- and
COx
- ions and HO- ion, respectively. The calculated electric
field strength in inhomogeneous electric field established on the needle tip
surface suggested that the abundant formation of NOx
- and
COx
- ions and HO- ion is attributed to the high field
strength at the tip apex region over 108 Vm-1 and the low field
strength at the tip peripheral region of the order of 107 Vm-1,
respectively. The formation of HO-, NOx
- and COx
-
has been discussed from the standpoint of negative ion evolution based on
the thermochemical reaction and the kinetic energy of electron emitted from
the needle tip. 相似文献
17.
An analytical method for DC negative corona discharge in a wire-cylinder device at high temperatures
《Journal of Electrostatics》2014,72(4):270-284
This paper proposes an analytical solution for DC negative corona discharge in a wire-cylinder device based on experimental results in which both the corona and drift regions are considered; this approach aims to provide a theoretical method for analyzing electrostatic precipitation at high temperatures. The inter-electrode space is divided into three zones, namely, the ionization layer, the attachment layer (corona region) and the drift region, to investigate the space charge concentration and the electric field distribution. The boundary of the ionization layer is assumed to be the radius at which the rate of ionization balances that of electron attachment. The radius where the value of E/N equals 110 Td is recommended as the boundary of the attachment layer. It was determined that an increasing temperature leads to a decrease in the largest space charge number density and the largest electric field in the drift region that can be provided by a discharging device. With respect to the device in the present work, when the temperature increases from 350 °C to 850 °C, the largest electric field decreases from ∼9 × 106 V/m to ∼3 × 106 V/m, and the largest charge number density decreases from ∼1.3 × 1015 m−3 to 6.4 × 1014 m−3. The radius of the corona region, the space charge number density and the electric field increase as the applied voltage increases at a given temperature. For example, at a temperature of 550 °C, when the applied voltage increases from 10,500 V to 18,879 V, the radius of the corona region increases from ∼2.9 mm to ∼4.9 mm. It appears to be unreasonable to use a constant value that is calculated from Peek's formula as the electric field at the surface of the cathode under all of the conditions. 相似文献
18.
A. K. Shuaibov L. L. Shimon A. I. Minya A. I. Dashchenko 《Journal of Applied Spectroscopy》1997,64(6):858-862
We present the results of investigations of the electrical and optical characteristics of a negative-polarity corona discharge
excited in systems of “pins-mesh” and “pins-plane” electrodes in a He/N2 mixture at atmospheric pressure. In order that such a corona discharge could be applied in systems of electric pumping of
the working medium of atmospheric-pressure N2-lasers, the optimum conditions should be: the total pressure of the mixture ≤150 kPa and the nitrogen pressure ≤5 kPa.
Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 290000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 6, pp. 837–840, November–December, 1997. 相似文献
19.
《Journal of Electrostatics》2006,64(7-9):525-530
The design of a micro-force sensor suitable for the measurement of corona drag and other low velocity drag studies in a small laboratory wind tunnel facility is described. Example drag data are given for dc corona discharge generated by sharp parallel electrodes mounted on a microscope glass slide with discharge parallel to the air flow. The arrangement simulates two-dimensional flow over a flat plate useful for theoretical analysis. Measurements of free stream wind velocities in the range 0–210 cm/s with attendant drag down to 10−7 N can be detected in this facility depending on the calibration. The force sensor utilizes two strain gages mounted on a 0.127 mm stainless steel “feeler gage” in a cantilever arrangement. A bridge circuit provides sensitivities in the range 40–250 N/mV using a gravitational calibration technique. Anomalous effects from suspension wires and the interaction of electrostatic forces with the surroundings are discussed. 相似文献
20.
在常压空气中,利用OES技术检测到负直流电晕放电等离子中激发态N原子发射光谱,并利用相对谱峰强度最大的674.5nm N原子激发跃迁谱线研究了相关空气参数和电参数对其相对密度的影响。结果表明,电离区内N原子相对密度随注入功率的升高呈增加趋势;随电极间距和相对湿度的增加,其相对密度逐渐减小;随N2流量增加,其相对密度呈先增加再减小趋势。在实验条件下,当针尖轴向距离r=1mm时,N原子相对密度出现最大值。 相似文献