An empirical model for ionic wind generation by a needle-to-cylinder dc corona discharge

We present the results of an experimental study on ionic wind generation by a needle-to-cylinder dc corona discharge. A strong electrical field in the air generates air flow driven by the motion of ionized gas molecules along electric field lines. We measured the ionic wind velocity and discharge current with respect to various electrode geometries, distances between electrodes, and applied voltages. Our measurements suggest an empirical model for the ionic wind velocity as a function of the geometric factors of the collector electrode and the applied electric potential, which is useful for designing ionic wind cooling systems for small electronics.     

On the negative corona and ionic wind over water electrode surface

The DC corona discharge in air and the induced ionic wind were investigated in the needle-to-water system at atmospheric pressure. The water deformation was measured under various conditions, and wind pressure and active areas were estimated accordingly. The effects of applied voltage, gap spacing and tip radius on the corona ionic wind were studied and the qualitative analysis was provided. Self-rotation of corona discharge was observed in experiments. The results show that higher voltage or electric field strength results in a stronger ionic wind. The active area increases with applied voltage below a voltage threshold. There is an optimal gap distance for a wider as well as stronger ionic wind and blunter needle we used leads to an enhancement on both the active area and the wind strength. The wind velocity reaches 7 m/s at optimized condition in the present system. The rotation of corona discharge helps to improve the active area and uniformity of the treating area which may be associated with the chemical reaction of the water surface.     

Analysis of geometric scaling of miniature,multi-electrode assisted corona discharges for ionic wind generation

The assisted corona discharge is a unique discharge configuration that utilizes multiple collecting electrodes to minimize the voltage required to initiate a corona discharge and to generate an ionic wind. In this work, the geometric parameters that govern the formation of the assisted corona discharge and subsequent ionic wind are evaluated. Flow velocity measurements suggest that the geometry of the electrode spacings is optimized for ionic wind generation when the current flowing to the collector electrode is maximized, and that as the electrode gap is decreased to microscale dimensions, ionic wind production is inhibited.     

Numerical simulation of conductive particle behaviour at the surface of a plate electrode affected by a DC corona field

The electric field in certain electrostatic devices can be modeled by a grounded plate electrode affected by a corona discharge generated by a series of parallel wires connected to a DC high-voltage supply. The system of differential equations that describe the behaviour (i.e., charging and motion) of the conductive particle in such an electric field has been numerically solved, using several simplifying assumptions. Thus, it was possible to investigate the effect of various electrical and mechanical factors on the trajectories of conductive particles. This model has been employed to study the behaviour of coal particles in fly-ash corona separators.     

Combustion of ethanol fuel droplet in vertical direct current electric field

Flame is affected by an external electric field because it contains ions and electrons related to chemical reactions. On the other hand, the movement of ions and electrons affects the external electric field due to their charge. This paper reports the combustion experiments of ethanol droplets in vertical electric field with variable distance electrodes apparatus in order to discuss the change of the external electric field due to the existence of flame. From a one-dimensional steady-state analysis, if the electric field is changed spatially, its effect on combustion behavior is aligned with V²/L³ and not V/L, where V is the applied voltage between electrodes, and L is distance between the electrodes. The droplet is burned between the two horizontal parallel electrodes. The flame deformation and the electric current are characterized by various electrode distances, and respectively, applied voltages. The vertical electric field induces a body force downwards on the flame. The flame deforms downward in the electric field because the electric body force counters the natural buoyancy. The relation between the applied voltage and electrode distance is investigated when the flame becomes vertically symmetrical and the results show that the deformation is the function of V/L^1.5. This indicates that the change in the electric field should be considered to discuss the effect of an external electric field on combustion behavior. The experimental results are rearranged using εV²/L³ where ε is electric permittivity of air because its unit is N/m³ and it considered to be the representative electric body force. Although its application is limited, qualitatively it can help to explain the experimental results of a droplet combustion. In addition, the degree of electron attachment to neutral molecules is discussed to interpret our experimental results.     

Electrohydrodynamic force produced by a corona discharge between a wire active electrode and several cylinder electrodes – Application to electric propulsion

Low-speed electric propulsion systems for long-duration near-space travels by using solar energy could be based on the electrohydrodynamic force produced inside a corona discharge. This paper is a contribution to a better understanding of these types of thrusters, in order to enhance the produced thrust and their electromechanical effectiveness. Three different simple designs are experimentally studied and compared. The first one is composed of a wire active electrode and a single cylinder grounded one. For the second three-electrode design, the single grounded cylinder is replaced by two cylinders. Finally, the last design is composed of an active wire supplied by a positive voltage, two grounded electrodes and two others cylinders at a negative voltage. On one hand, results show that the use of two grounded electrode instead of a single one results in an increase of the discharge current. Moreover, whatever the electrode gap d, the current-to-thrust conversion is more effective with the three-electrode design. It changes from 31 to 58 N/A (+87%), from 74 to 85 N/A (+15%), and from 104 to 120 N/A (+15%), for electrode gaps d = 10, 20 and 30 mm, respectively. The thruster effectiveness θ is improved by 2 mN/W. On the other hand, the use of two collecting electrodes supplied by a negative high voltage does not result in an effectiveness enhancement because the power consumption is significantly increased.     

Influence of wire mesh electrodes on the volume and surface characteristics of dielectric barrier discharge of atmospheric pressure helium

The dielectric barrier discharge of helium in a 6 mm gap at atmospheric pressure was studied. In this paper, the influence of electric field distribution on the uniformity of DBD is analyzed theoretically and verified by experiments. The experimental results show that the mesh electrode produces a local enhancement effect by affecting the electric field and then produces corona discharge, which provides seed electrons for the subsequent discharge process. The effects of mesh diameter and size on discharge uniformity and stability are analyzed, the electrode structure parameters are optimized, the method of a segmented electrode is proposed, and the discharge process and charge distribution are studied. The electrical diagnosis results of plasma technology show that the segmented mesh electrode reduces the breakdown voltage of DBD and increases the charge deposition.     

Experimental study of a modified dual-type high-voltage electrode for electrostatic separation applications

Several electrode arrangements have been proposed to enhance the efficiency of insulating materials charging by corona discharge. Recent studies pointed out that the presence of metal strips in the proximity of a dual-type high voltage electrode increases the total current measured at the surface of the collecting electrode, decreases the corona onset voltage value and enlarges the reparation of current density as well. The aim of this paper is to evaluate the benefits of using such an electrode arrangement for corona charging of non-conductive particulate materials in belt-type corona-electrostatic separators. The experimental study was carried out with samples of Aluminum and Polystyrene particles in the size class 125–250 μm. The presence of grounded strips reduces the electric wind, which is associated to corona discharge but not tolerated in such processes that involve micronized materials. At the same time, it improves the corona charging conditions of non-conductive materials and as consequence the overall efficiency of the corona-electrostatic separation process. The use of the new electrode configuration is characterized by both high recovery rates and better purities of the separated products.     

Study on both discharge and charging of the earthed atomizing corona discharge and the influence of magnetic fields on them

In the paper, the influences of water flux on both discharge current and onset voltage were studied. Both charging and capturing particles of atomizing corona discharges were investigated when the magnetic field was used or not. The charge number of droplets and their sizes were calculated after some parameters were measured by Millikan oil drop instrument. In addition, the capturing ability of atomizing corona discharge pre-charger with magnetic field was compared with the traditional pre-charger. Eventually, the charging mechanism of atomizing corona discharge with magnetic field was analyzed through the above-mentioned experimentation and comparison. The result shows that the smallest onset voltage will appear with water flow increase in the atomizing corona discharge, and that the ion concentration between electrodes is the highest in the atomizing corona discharge charger with magnetic field than any other pre-charger, which is conducive for charging dust particles. Hence the new pre-charging technique is promising for capturing fine aerosol particles in electrostatic precipitators.     

The production of excimer molecules and excited atoms in a positive corona discharge in He/Xe(Kr)/SF6/CCl4 mixtures

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.     

基于电晕放电的大功率LED散热研究

针对大功率LED芯片的散热问题,提出了一种基于电晕放电原理的离子风散热方案。通过试验,研究了电晕放电的电学性能,同时探寻了放电电压对制冷效果的影响以及温降随电晕放电功率的变化规律。结果表明,放电间距相同时,对发生器施加负电晕能够在较低的电压下产生离子风,降温效果显著。电晕电流平方根与放电电压呈线性关系。电晕放电功率为1.5 W、放电间距为10 mm时,散热效果最好。     

120 kV下常压空气纳秒脉冲电晕放电特性

使用上升沿15 ns、脉宽30~40 ns的重复频率纳秒脉冲电源对120 kV下大气压空气中管-板电极结构电晕放电进行了实验研究,通过电压电流测量、放电图像拍摄和X射线探测分析了纳秒脉冲电晕放电特性。结果表明:纳秒脉冲电晕放电中存在X射线辐射,但辐射强度较弱,X射线辐射计数随着气隙距离的增大而减少,随着脉冲重复频率的增大而增多;放电空间的残余电荷加强了下一个脉冲到来时的局部电场,从而导致高重复频率下易于出现分散的电晕通道。     

The Effect of the Polarity and Design of the Discharge System on the X-ray Spectrum of the Micropinch Discharge Plasma

The spectral composition and X-ray radiation yield of a micropinch discharge plasma obtained at a facility of the low-inductance vacuum spark type are studied as a function of the polarity and design of the electrodes of the discharge system. It is shown that the X-ray radiation of the micropinch discharge plasma depends on the configuration of the electric field in the interval between the discharge electrodes, which determines the amount of erosion products involved in the micropinch process, resulting in the increase in the plasma density and its radiative characteristics.     

Negative Corona Discharge Ion Source Under Ambient Conditions with Mini Line-cylinder Electrodes

提出了一种新型的可在大气环境下工作的离子源．该离子源通过电晕放电产生离子,为线-筒结构,由内电极和外筒电极组成,电极半径分别是0.16和4 mm．采用了一系列夹持方法,保证了内外电极具有较高的同轴度．设计了一套进样系统,可以控制进入离子源的样品浓度．给出了放电启动电压的计算公式．实验表明,在大气环境条件下可以很好地电离甲酸、乙酸等负电性的化学物质．为了减小离子源的体积,引入了微机电系统技术．改进了原线-筒型结构以防止随之而来的沿面放电．该离子源接口简单,可广泛应用于质谱仪、MMS、IMS和FAIMS上．     

线-铝箔电极电晕放电激励器的推力理论与实验研究

空气电晕放电离子风激励器无需旋转部件, 仅通过消耗电能就能直接产生驱动力, 它是一种新型的动力技术, 备受国内外航空航天界的广泛关注. 目前对空气电晕放电离子风激励器的推力产生机理虽有各种解释, 但是现有理论均不能统一各种条件下的实验结果, 仍需要开展进一步的分析与研究. 本文以线-铝箔电极电晕放电激励器为研究对象, 通过实验研究发现作用在线电极与铝箔电极上的静电力不对称, 而且改变铝箔电极纵向高度和气压均能影响激励器的推力大小; 通过理论分析, 考虑电晕层与空间电荷的影响, 建立了线-铝箔电极电晕放电激励器的推力计算模型, 其计算值与实测值比较一致. 基于上述实验现象与理论建模分析, 本文认为线-铝箔电极电晕放电激励器的推力主要来源于线电极电晕产生的空间电荷对电极系统产生了不对称静电力作用, 使激励器出现净静电力作用.     

The correlation between corona current distribution and collection of fine particles in a laboratory-scale electrostatic precipitator

An analysis of the electrostatic gas cleaning fundamental phenomenon shows an essential influence of discharge electrode construction on the gas cleaning process efficiency.In the physical model tests there were used rigid discharge electrodes with corona emitting elements of various geometries. Different constructions of discharge electrode were tested in the aspect of discharge current uniform distribution on collecting electrode surfaces. Measurements of discharge current distribution has been carried out for discharge electrodes with different spike shapes and in different electric field geometry. The research aim was to determine the optimal discharge electrode construction ensuring high collection efficiency of fine particles. Collection efficiency measurements of selected fly ash samples (from coal fired boilers) were carried out on a laboratory testing bench in a horizontal electrostatic precipitator model.     

Computational study of glow corona discharge in wind: Biased conductor

Corona discharges in flowing gas are of technological significance for a wide range of applications, ranging from plasma reactors to lightning protection systems. Numerous experimental studies of corona discharges in wind have confirmed the strong influence of wind on the corona current. Many of these studies report global electrical characteristics of the gaseous discharge but do not present details of the spatial structure of the potential field and charge distribution. Numerical simulation can help clarify the role of wind on the ion redistribution and the electric field shielding. In this work, we propose a methodology to solve numerically for the drift region of a DC glow corona using the usual approach of collapsing the ionization region to the electrode surface, but allowing for strong inhomogeneities in the electrical and flow setup. Numerical results for a grounded wire in the presence of an ambient electric field and wind are presented. The model predicts that the effect of the wind is to reduce the extension of the corona over the wire and to shift the center of the ion distribution upstream of the flow. In addition, we find that, even though the near-surface ion distribution is strongly affected by the ion injection law used, the current characteristics and the far field solution remain pretty much unaffected.     

Effect of relative humidity on current–voltage characteristics of monopolar DC wire-to-plane system

This paper deals with the DC monopolar corona discharge in wire-to-plane geometry under variable humid air conditions. The classical formulas of Townsend commonly used for the current–voltage characteristics were used to determine the various corona parameters for the both polarities of the corona discharge. A circular biased probe has been adapted to the plane and is used to measure the ground plane current density and electric field during the monopolar corona discharge. A new approach to the problem of corona discharge in transmission system has been described in this paper. The effect of varying the humidity and wires diameter is also investigated. The values of the electric field and the current density are maximum beneath the corona wire and decrease when moving away from them and the current–voltage characteristics follow the quadratic Townsend's law. The experimental results show that the monopolar corona discharge is strongly affected by the air humidity. The current density and the electric field are measured and compared with the computed values. The agreement between the calculated values and those obtained experimentally is satisfactory. The per unit electric field and current density are also represented by a unique function.     

Sulfur dioxide (SO2) gas transfer process enhanced by corona discharge

The sulfur dioxide (SO₂) gas transfer process in a corona discharge field has been studied. The experiments were conducted to investigate the effects of voltage, length, and height of the discharge area on the electric transfer of SO₂ as well as on the desulphurization efficiency. Experimental results show that corona discharge can facilitate the SO₂ gas transfer process. The rate and efficiency of desulphurization increase with increasing voltage, length of discharge area, and input power. The addition of a uniform electric field to the corona-discharge field improves the electronic transfer of SO₂. Measured desulphurization efficiency was as high as 95%, and the augmentation of desulphurization efficiency due to corona discharge was nearly 50% under the conditions tested.