实现大气压负直流辉光放电的针-柱电极结构设计与实验

为了实现大气压环境下稳定的辉光放电,设计了一种新型的针-柱电极结构放电装置。采用针尖直径为56.4 μm的不锈钢针作为放电阴极,直径为4 mm的紫铜圆柱作为放电阳极,两者通过精密机械结构保持平行。当针-柱之间间距为2 mm、镇流电阻10 MΩ,放电电阻10 MΩ,测试电阻1 kΩ、放电电压-2 740 V、大气压环境、室温、无外部通入气流时,针-柱之间实现了稳定的辉光放电。示波器存储的放电波形和数码相机记录的放电图像验证了从电晕放电到辉光放电,再到火花放电的三种放电模式。该针-柱结构易于用MEMS工艺加工制作,可应用于便携式分析仪器中作为离子源使用。     

针-板DBD微流注与微辉光交替生成的机理研究

在介质阻挡放电体系中产生辉光放电可以有效的提高放电体系产生高能电子的性能, 为等离子体化学反应提供更加丰富的活性粒子.本文对针-板介质阻挡放电体系下的放电模式进行了研究,实验发现放电正负半周期表现出不同的放电模式, 激励电压为3 kV时放电正负半周期分别为微流注放电和电晕放电(或者Trichel脉冲放电),激励电压为6 kV时放电正负半周期分别为微流注放电和微辉光放电.微辉光放电形貌具有与典型辉光放电相同的分层次放电结构, 分析了激励电压6 kV时的放电过程,认为足够强的阴极电场强度和裸露针状电极形成的有效的二次电子发射过程是形成微辉光放电的主要因素,绝缘介质层的存在避免了微辉光放电向弧光放电过渡.     

Numerical analyses of a viscid compressible ionic flow

The aim of the paper is to investigate numerically the effect of a DC positive corona discharge between two parallel wire electrodes of different diameter along an insulating aerofoil surface in low subsonic compressible flow. The modeling takes into account the two characteristic regions of the phenomenon: the corona sheath, surrounding the smaller diameter electrode, and the ion drift zone. The electric force is modeled by a simplified form of the electromagnetic tensor via the coupling between Electrostatic and Navier–Stokes equations. The corona discharge system is effective in preventing flow separation, reducing total aerofoil drag and enhancing the heat and mass transfer between aerofoil and the surrounding flow.     

酮类有机物放电离子淌度谱研究

离子淌度谱是一种快速检测痕量挥发性有机物的高灵敏方法。在放电离子源离子淌度谱装置上,研究了八种酮类有机物的离子淌度谱。实验测量了各种离子的约化迁移率,其中丙酮、正丁酮、1-甲基-2-吡咯烷酮、环己酮、苯乙酮的实验结果与前人63Ni放射源离子淌度谱相一致,而甲基异丙基酮、4-甲基-2-戊酮、环戊酮单体和二聚体离子的约化迁移率则是首次报道。实验测量的约化迁移率与离子质量线性相关,获得的对酮类有机物检测灵敏度在ng·L-1量级。     

The study of the ionic wind blower with multi-needles/ring type electrodes disposed on inner wall of the cylindrical blower

Corona discharge is one of many methods that convert electrical power into mechanical force. It has been studied for various industrial fields because of its many advantages over conventional motor, such as its no moving parts, simpler structure, minimizing size and so on. In this paper, a discharge system with multiple corona electrodes disposed in a ring format, is studied by focusing on the electrical and mechanical characteristics. Effective ionic wind generation is due to the corona discharge which depends on electric field. Therefore, the electric field is affected by the voltage, discharge spacing, and distance between each corona electrodes.     

Dielectric Barrier Discharge in Analytical Spectrometry

Abstract

Dielectric barrier discharge is a nonequilibrium plasma, and its industrial application has been on a large scale. Similarly, its prominent features of high dissociation ability at low working temperature and low power consumption, simple and adjustable configuration, ambient working conditions, and long lifetime are favorable for developing a wide array of analytical devices as well. This review addresses the basics of dielectric barrier discharge and emphasizes their analytical applications in analytical atomic spectrometry, chemiluminescence, gas chromatographic detectors, ion source for mass spectrometry, and ion mobility spectrometry with 103 references.     

X-ray photoelectron spectroscopy,X-ray excited Auger electron spectroscopy and time-of-flight secondary ion mass spectroscopy characterization of carbon fibres activated by d.c. corona discharge at ambient pressure and temperature

High modulus polyacrylonitrile-derived fibres were characterized by X-ray photoelectron spectroscopy, X-ray excited Auger electron spectroscopy and time-of-flight secondary ion mass spectroscopy after d.c. corona discharge treatments under a nitrogen atmosphere at ambient pressure and temperature. The results allow identification of the main functional groups produced by the treatment on the fibre surface and verification of a substantial equivalence of negative- and positive-corona discharge treatments.     

Experimental observation of negative differential characteristic of corona discharge in ultraviolet spectrum

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.     

Characteristics of DC discharge in a wire-cylinder configuration at high ambient temperatures

In the present work, the characteristics of direct-current (DC) discharge in a wire-cylinder configuration at an ambient temperature range of 350–850 °C were studied by analyzing photographs of the discharging process and the corresponding V–I characteristics, with the aim of facilitating the application of plasma technology in the fields of energy and the environment. The influences of the ambient temperature, the inter-electrode gap, the gas medium and the cathode material on the DC discharge were investigated. The corona-onset threshold voltage (COTV) and the spark-breakdown threshold voltage (SBTV) decrease as the ambient temperature increases, and the SBTV decreases more rapidly. Increasing the inter-electrode gap enlarges the difference between the SBTV and the COTV. After spark breakdown, in an air atmosphere, glow discharge is more likely to take place under conditions of high ambient temperatures or small inter-electrode gaps. The values of the SBTV in different atmospheres have the following relation: air ≈ O₂ > CO₂. At an ambient temperature range of 350–850 °C and in an atmosphere of N₂, glow discharge and arc discharge occur successively as the output voltage of the power supply is increased, while in an atmosphere of O₂ and CO₂, only corona and arc discharge are successively observed. In an air atmosphere, when the inter-electrode gap is 29 mm, corona, glow and arc discharge occur successively with increasing output voltage when the ambient temperature is 850 °C, while only corona and arc discharge appear when the temperature is 350–750 °C. When the inter-electrode gap is 5 mm in an air atmosphere, corona, glow and arc discharge occur successively in an ambient temperature range of 350–850 °C. The cathode material has a minor influence on the COTV and a more significant influence on the SBTV. In a device using a cathode with a low work function, the SBTV is low, and the power to maintain arc discharge is small.     

Current analysis of DC negative corona discharge in a wire-cylinder configuration at high ambient temperatures

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.     

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.     

Modelling of an improved positive corona thruster and actuator

In this work we are going to perform a simulation of a positive corona discharge in nitrogen gas, using two different asymmetric capacitor geometries. We intend to increase the highest ion wind velocities and electrostatic propulsion forces on the considered structures. In our model, the used positive ion source is a small diameter wire, which generates a positive corona discharge directed to the ground electrodes. By applying the fluid dynamic and electrostatic theories, all hydrodynamic and electrostatic forces will be computed in an attempt to demonstrate the greater performance of the new developed geometries.     

Modulation effect produced by adjacent AC voltage on the characteristics of negative corona current pulses in a wire-cylinder electrode configuration

In this paper, a wire-cylinder electrode system was designed to study the negative DC corona pulses due to the influence of AC voltage applied to an adjacent conductor. The corona onset voltage and distribution pattern and the parameters of the corona current pulses such as the rise time, pulse duration and the average pulse amplitude are systematically analyzed. The AC voltage is found to have an interesting modulation effect on the time interval of the current pulses. At last, based on a simplified ion cloud model, a full explanation is given to reveal the mechanism behind the influence of the AC voltage on negative DC corona.     

Effect of air flow on corona discharge in wire-to-plate electrostatic precipitator

This paper analyses corona discharge in ambient air with laboratory-scaled wire-to-plate electrostatic precipitator (WPESP). The electric field is behind the electro hydrodynamic (EHD) flow in air. Its measurements provide complementary results for the corona discharge study because the classical theory based on the current and voltage data is unsatisfactory. Taking into account the dynamic air flow velocity is perpendicular to the active wires, measurement method of the positive and negative DC corona current density and electric field, has been introduced. It has been shown also that the dynamic air flow velocity modifies the current density and the electric field distributions on the planes surfaces of the WPESP.     

空气电晕放电中的OH自由基发射光谱

测量了大气压下向空气中喷射不饱和水蒸气的电晕放电产生的OH自由基的发射光谱。通过对光谱线强度变化的分析,研究了电场强度、放电方式、水蒸气比例等因素对OH自由基产生过程的影响,及OH自由基浓度在放电反应空间的分布特点。     

Influence of the corona-wire diameter and length on corona discharge characteristics of a cylindrical tri-axial charger

In this paper, the corona discharge characterization in terms of current–voltage relationships of a unipolar cylindrical tri-axial charger on the effects of the corona wire diameter and length have been experimentally studied and discussed. A commercial computational fluid dynamics software package, COMSOL Multiphysics™, was used to predict the electric field distribution in the ion generation and charging zones of the charger and the ion penetration through the perforated screen opening on the inner electrode of the charger. It was found from experimental results that both positive and negative charging currents in the charging zone of the charger increased with increasing corona and ion-driving voltages. At the same corona and ion-driving voltages, both positive and negative coronas were decreased with increasing diameter of the corona-wire. Compared with the corona-wire of 22 mm in length, the magnitude of both positive and negative charging currents were markedly higher for corona-wire of 11 mm in length at the same corona voltage. It was found that the charging currents for negative coronas were about 1.2 times higher than those positive coronas at the same corona and ion-driving voltages. Numerical results of the electric field distribution and the ion and charged particles migrations in the discharge and charging zones of the charger is correlated to have the same direction with the experimental results of the current–voltage relationships. Also, this can be used to guidance in describing the electric field distribution and the behavior of ion and charged particle trajectories that cannot be seen from experiments in order to improve the applicably design and refinement of a unipolar cylindrical tri-axial charger.     

利用密度反馈实现离子源长脉冲放电

 介绍了等离子体密度对离子源放电的影响,为了获得长脉冲放电,采用朗缪尔探针测量等离子体密度并反馈调节离子源放电。基于朗缪尔探针测量,设计了控制部分硬件与软件构架,建立了离子源等离子体密度反馈控制系统,并成功地应用于离子源等离子体放电实验,通过反馈调节实验进气,得到了长达4.5 s的长脉冲放电,为中性束注入稳态运行提供了依据。     

Sliding discharge in air at atmospheric pressure: electrical properties

Several studies have shown that a surface non-thermal plasma may be used as an electrofluidodynamic actuator for airflow control. For few years, we has been working on this subject, especially in the case of DC corona discharges and AC barrier discharges established at the wall of profiles. The present paper deals with a new type of surface plasma using a sliding discharge. This discharge, excited here by a negative AC voltage with a positive DC component, is created in a three-electrode geometry: one DC positive electrode and two negative AC electrodes at the same voltage. Then a barrier discharge is established between the positive electrode and the first negative one when a surface corona discharge or sliding discharge is generated between the positive electrode and the second negative one. In this preliminary study, the goal is to obtain a stable sliding discharge. Then the electrical properties of this discharge are observed and briefly discussed.     

Effect of corona discharge on cadmium sulphide and lead sulphide films

This paper describes the effect of corona discharge on cadmium sulphide (CdS) and lead sulphide (PbS) films prepared using the chemical route. The property of films before and after exposure to corona has been described in detail. The electronic properties of the CdS and PbS films have been studied by current-voltage (I-V), capacitance-voltage (C-V) measurements. The structural properties and surface morphology were studied by using X-ray diffraction and scanning electron microscopy before and after exposing to Corona discharge. The films displayed the change in surface morphology after exposure to the corona discharge. It has been found that the films showed an increase in resistivity after exposure. This change in property has been attributed to modification in surface states. Time-dependent recovery indicated that room temperature annealing is sufficient to regain the normal resistivity of the films. The experiment was carried with the aim of studying the effect of the interaction of corona discharge on the semiconductor films and its subsequent effects.     

Effect of needle cone angle and air flow rate on electrostatic discharge characteristics of a corona-needle ionizer

In this study, the corona-needle ionizer was designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current–voltage relationships of the corona ionizer, including the effects of discharge electrode cone angle and air flow rate were presented. It was found that the charging current and ion concentration in the charging zone increased monotonically with corona voltage. Conversely, discharge currents decreased with increasing angle of the needle cone. The negative corona was found to have higher current than the positive corona. At higher air flow rates, the ion current and concentration were found to be relatively high for the same corona voltage. The effect of air flow rate was more pronounced than the corona voltage. It was also shown that the ion penetration through the ionizer decreased with increasing corona voltage, and increased with increasing air flow rate. The highest ion penetration through the ionizer of the 10° needle cone angle was found to be about 93.7 and 7.7% for positive and negative coronas, respectively. The highest ion penetration for the needle cone angle of 20° was found to be 96.6 and 6.1% for positive and negative coronas, respectively.