DC corona discharge ozone production enhanced by magnetic field

We have studied the effect of a stationary magnetic field on the production of ozone from air at atmospheric pressure by a negative corona discharge in a cylindrical electrode configuration. We used a stainless steel hollow needle placed at the axis of the cylindrical discharge chamber as a cathode. The outer wall of the cylinder was used as an anode. The vector of magnetic induction was perpendicular to the vector of current density. We found that: (a) the magnetic field extends the current voltage range of the discharge; (b) for the discharge in the Trichel pulses regime and in the pulseless glow regime, the magnetic field has no substantial effect on the discharge voltage or on the concentration of ozone that is produced; (c) for the discharge in the filamentary streamer regime for a particular current, the magnetic field increases the discharge voltage and consequently an approximately 30% higher ozone concentration can be obtained; (d) the magnetic field does not substantially increase the maximum ozone production yield. A major advantage of using a magnetic field is that the increase in ozone concentration produced by the discharge can be obtained without additional energy requirements.     

Kinetics of microplasma atmospheric ion generation correlated with discharge current

The conditions necessary for achieving a stable bipolar ion generation (in the order of 10⁶ ion/cm³) and lower ozone concentration (less than 50 ppb) using a surface discharge microplasma device (SMD) by adjusting the applied voltage and frequency were experimentally determined and investigated. Measurements of the discharge current characteristics of the SMD revealed saturation against the frequency (1.5–2.5 kHz, depending on the applied voltage). The ion and ozone concentrations both increased in step with the discharge current in the lower frequency region. The ion concentration reached equilibrium in the frequency range of 200–500 Hz, and the point of equilibrium within that range depended on the applied voltage. The ozone concentration did not reach equilibrium under our experimental conditions (ozone concentration < 100 ppb). The kinetics of the ion/ozone generation rate with a focus on the plasma reaction and recombination of bipolar ions is discussed.     

Numerical modeling of ozone production in a pulsed homogeneousdischarge: a parameter study

The pulsed volume discharge is an alternative for the efficient generation of ozone in compact systems. This paper presents a parameter study of the reactions in this kind of homogeneous discharge by using a numerical model which solves plasma chemical kinetic rate and energy equations. Simulations are performed for 10^-9-10^-5 s single pulses and oxygen gas density in the range 10<300 K and normalized electric field of 1000 decreased. The maximum concentration is 3% at 10 amagat and 100 K. The results on ozone accumulation in multiple pulse discharges are presented. In contrast to the single pulse case, higher efficiency is achieved at lower gas density. This scaling can be explained by losses due to ion currents     

Effective ozone generation utilizing a meshed-plate electrode in a dielectric-barrier discharge type ozone generator

A meshed-plate electrode, an alternative to the conventional plate electrode of the dielectric-barrier discharge (DBD) ozone generator, has been studied in order to show the effectiveness of the meshed-plate electrode in improving ozone generation. A DBD ozone generator with mesh electrode is shown to have the following two advantages: First, such a device produces corona at its thin, sharp edges, thereby decreasing corona onset voltage for a given gap spacing. Second, by utilizing the air-voids of the meshed-plate electrode, the dense ozone produced in the small, high temperature gap region of the DBD can escape rapidly to the low temperature region. As a result, decomposition of the ozone can be reduced. In this study, surface discharge, meshed-plate electrode, and conventional DBD ozone generators are studied and compared experimentally. The maximum ozone generation concentration and ozone generation efficiency are obtained with the meshed-plate type electrode.     

Macrokinetic study on ozone boundary concentration. Effect of temperature

The process of ozone production in pure oxygen using the tubular, high voltage pulse supplied ozonizer was studied. The unusual methodology of conducting kinetics measurements of the ozone synthesis process was presented. It was shown how the process rate changes along the discharge gap. The effect of power density and gas residence time in the discharge gap on the process rate was analysed. The temperature influence on the course of the process, particularly on the ozone boundary concentration and ozone decomposition rate constant, was discussed.     

气液滑动弧等离子体降解高浓度有机废水的研究

采用气液滑动弧放电非平衡等离子体进行降解高浓度苯酚模拟废水(初始浓度为872 mg／L)的研究。实验研究表明:由于液滴的存在改变了电极间的介电常数和局部电场,气液滑动弧放电的电压波形比纯气流滑动弧放电更加不规则,起弧电压更低;采用氧气作为载气能提高苯酚的降解效果,最后TOC值为44 mg／L;增大气液混合比,相应的加强了废水的雾化效果,增大水气接触表面积,进而提高了苯酚的降解效果;在尾气中检测到CO2的存在,最高浓度达到35357 mg/m3。     

颗粒填充对介质阻挡放电制臭氧性能的影响

在同轴圆柱单介质内外双水冷结构的DBD臭氧发生器的放电间隙内分别填充玻璃珠、高铝瓷、石英砂和熔融石英砂等颗粒,研究填充颗粒材料、粒径大小、间隙宽度等参数对臭氧生成效率的影响。结果表明：颗粒材料的介电常数是影响其臭氧制取效果的主要因素,随着介电常数的增加,间隙击穿电压降低,但由于颗粒导致电场的畸变,间隙折合场强增加,臭氧生成的最大能效降低,饱和浓度提升;高铝瓷具有最高的臭氧饱和浓度,与未填充的空床相比,饱和浓度提升136%;对于填充不同粒径熔融石英砂颗粒,随着粒径的增加,间隙击穿电压上升,间隙的折合场强提高,臭氧生成的最大能效降低,而饱和浓度提升;通过在宽间隙内填充介质颗粒可以得到窄间隙宽度的臭氧制取效果。     

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在同轴圆柱单介质内外双水冷结构的DBD臭氧发生器的放电间隙内分别填充玻璃珠、高铝瓷、石英砂和熔融石英砂等颗粒,研究填充颗粒材料、粒径大小、间隙宽度等参数对臭氧生成效率的影响.结果表明:颗粒材料的介电常数是影响其臭氧制取效果的主要因素,随着介电常数的增加,间隙击穿电压降低,但由于颗粒导致电场的畸变,间隙折合场强增加,臭氧生成的最大能效降低,饱和浓度提升;高铝瓷具有最高的臭氧饱和浓度,与未填充的空床相比,饱和浓度提升136％;对于填充不同粒径熔融石英砂颗粒,随着粒径的增加,间隙击穿电压上升,间隙的折合场强提高,臭氧生成的最大能效降低,而饱和浓度提升;通过在宽间隙内填充介质颗粒可以得到窄间隙宽度的臭氧制取效果.     

氮气交流放电光谱强度和电压及气压的关系

利用浓度调制光谱技术,测量了玻璃管中放电频率20 kHz时N2的介质阻挡放电光谱.实验记录了N2的C3∏u-Bb∏g357.7nm和B2∑ u-X2 g391.4 nm的跃迁谱线光谱强度随小同电压和气体压强变化规律.实验数据显示,保持气体压强p=130 Pa不变,在电压较低时,光谱强度随电压增长较快,在电压较高时,光谱强度增长较慢;保持放电电压U=6.4 kV不变,光谱强度随气压增长逐渐变小.根据电子和分子碰撞激发函数和电离函数,建立光强随放电参数变化的物理理论模型和公式,并对实验数据进行数学拟合,拟合曲线与实验结果符合较好,相关系数R>0.9.进一步明确了等离子体发射光谱强度随不同电压和气体压强变化的机理.     

Formation of reactive species in gliding arc discharges with liquid water

The effects of gas composition on gliding arc (glidarc) electrical discharge reactors with pure water have been studied. The glidarc reactors utilized AC electrical discharges with two different electrode configurations. In one case a set of two stainless steel electrodes connected to a single power supply was placed in the gas phase over the liquid surface (power=250–300 W, maximum voltage=12 kV). The second experimental arrangement utilized a reactor with a set of three stainless steel electrodes supplied by two identical high-voltage transformers, where the electrodes were placed over the water surface or with the water sprayed directly in the plasma formed between the electrodes (power=500–600 W, maximum voltage=12 kV). The variation of pH and conductivity and the formation of hydrogen peroxide, ozone, nitrate, and hydrogen were measured. The effects of the type of gas, including pure oxygen, pure nitrogen, and dry air, were determined.     

电激励脉冲HF激光SF_6/C_2H_6工作气体的放电特性

研究了电激励脉冲HF激光工作介质SF6/C2H6混合气体的放电特性。通过对放电等离子体荧光图像和放电波形的测量,分析比较了不同条件下放电稳定性、剩余电压、能量沉积效率等特性参数的变化情况。实验结果表明:混合气体的放电过程存在主放电、剩余电压维持和电弧放电3个阶段,各阶段的放电特性有所差异;提高充电电压有利于放电能量的有效沉积,也会使不稳定的电弧放电提前;增加C2H6原子分数能起到抑制电弧放电的作用;混合气体总压的增加会导致剩余电压的提高以及辉光放电的能量沉积效率的降低;最佳的能量沉积出现在电弧放电阶段与辉光放电阶段即将融合的临界状态。     

Double layer creation in asymmetric discharge

Particle-in-cell Monte Carlo code has been used to simulate the DC discharge in strongly inhomogeneous cylindrical and spherical electric fields. Such a discharge occurs in the gaseous medium between a thin wire and a coaxial cylinder, or between a sharp tip and a sphere at high voltage. The discharge threshold conditions have been specified and corresponding threshold voltage (threshold electric field intensity) has been determined numerically. The threshold voltage varies with the electrode geometry, the polarity of active electrodes, gas composition (H, Ar, N₂) and gas pressure. In case of a positively charged inner electrode, a thin boundary sheet is developed in the vicinity of the electrode, when the quasineutrality of the ionized gas is violated and the electron current is closed via the external RLC circuit. In the opposite case of a negatively charged inner electrode, a double layer is developed inside the ionized gas. Dedicated to Prof. Jan Janča on the occasion of his 60^th birthday. Presented at 23^rd International Conference on Phenomena in Ionized Gases, Toulouse (France), July 17–22, 1997. The work was supported by the Grant Agency of the Czech. Acad. Sci. under Contract No. 202/1022.     

相对湿度和氧气浓度对滑动弧放电特性影响研究

本文通过检测背景气体不同含氧量和相对湿度下的放电电流强度和臭氧浓度,分析氧气和水汽对滑动弧放电特性的影响.结果表明,背景中氧气是臭氧的主要发生源,臭氧随氧气浓度的增大而增大.水汽的离解反应与臭氧发生反应存在竞争关系,同时其生成的OH粒子会与臭氧发生反应,因此水汽对臭氧的产生起抑制作用.由于氧气和水的电子结合系数都很高,水与电子还会发生离解结合反应,因此背景气体氧气浓度和水汽含量增大会减少等离子体区域的电子数量,降低放电电流强度.     

Stability and energy efficiency of pulsed corona discharge in treatment of dispersed high-conductivity aqueous solutions

Pulsed corona discharge (PCD) is an energy-efficient method of water treatment, although its instability in treatment of conductive solutions showered onto the electrodes presents a problem. The impact of conductivity and gaseous ozone concentration on the discharge stability and the energy transfer efficiency was established. The discharge was stabilized by adjusting the voltage pulse shape. Energy dissipation increases with the treated solution conductivity due to ohmic losses reaching 30% of the energy delivered to the reactor at 45 mS cm⁻¹. The PCD energy efficiency and safety was improved by the modified electrode system design reducing the losses.     

Relaxing Phenomena in Negative Corona Discharge: New Aspects

Two theories, explaining the time dependence of the negative corona discharge current in air, are confronted with new experimental results. The influence of the ozone concentration on the discharge current was experimentally confirmed in dry air and in mixtures of nitrogen with oxygen. Assuming that only the dissociative electron attachment to ozone molecule is a process being responsible for a reduction of the electron component in the total mean discharge current, the mean value of the electron attachment rate constant k = (3 - 5.5) × 10^?9 cm^?3 s^?1 was derived from the measured dependence of the discharge current on the ozone concentration. The calculated value of the rate constant k corresponds to the dissociative attachment of electron to ozone molecule via process e + O₃ → products (O^? or O^?₂ negative ions).     

Output characteristics of a cataphoresis He–Sr recombination laser

A cataphoresis discharge tube of 7 mm inner diameter and 38 cm active length was designed and made for the He–Sr⁺ laser. The cataphoretic input of uniform distribution of strontium vapor concentrations along the active region was realized by the cataphoresis effect and the slow flowing (0.5 nl/h) of helium buffer gas. The strontium ionic recombination laser at 430.5 nm and the R–M transition laser at 1.03 μm were obtained with the modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The laser components are concentrated on the 430.5 nm wavelength. Dependences of working parameters such as the pulse frequency, the supply voltage, and the helium pressure on laser output characteristics were measured and discussed. The maximum laser output power of 819 mW and specific power of 56 mW/cm³ were obtained, respectively.     

Ultrashort electron beam and volume high-current discharge in air under the atmospheric pressure

Conditions are studied under which an electron beam and a volume discharge with a subnanosecond rise time of a voltage pulse are produced in air under atmospheric pressure. It is shown that the electron beam appears in a gas-filled diode at the front of the voltage pulse in ∼0.5 ns, has a half-intensity duration of ≤0.4 ns and an average electron energy of ∼0.6 of the voltage across the gas-filled diode, and terminates when the voltage across the gap reaches its maximum value. The electron beam with an average electron energy of 60 to 80 keV and a current amplitude of ≥70 A is obtained. It is assumed that the electron beam is formed from electrons produced in the gap due to gas ionization by fast electrons when the intensity of the field between the front of the expanding plasma cloud and the anode reaches its critical value. A nanosecond volume discharge with a specific power input of ≥400 MW/cm³, a density of the discharge current at the anode of up to 3 kA/cm², and specific energy deposition of ∼1 J/cm³ over 3 to 5 ns is created.     

横向表面放电光泵浦源特性研究

 介绍了一种用以泵浦XeF(C-A)激光的横向表面放电辐射源,比较详细地研究了这种泵浦源的放电击穿特性、放电电流与充电电压及不同气体介质的关系、表面放电均匀性以及不同气体成分对表面放电辐射特性的影响。得到了放电击穿时间、放电峰值电流随充电电压、不同气体介质变化的曲线;分析了提高放电均匀性的途径,在电极长50cm、间距6cm、充电电压25kV条件下获得了均匀放电。获得了各种实验条件下放电辐射的光谱曲线;通过对辐射光谱的分析,研究了有利于光解离XeF₂的最佳实验条件,当p_Ar:p_N2=1:1时,放电在远紫外波段产生的辐射最强。     

大气压氦气多路低温等离子体射流

为了研究大气压低温等离子体多路射流阵列的放电特性,设计一个实现7路低温等离子体射流的放电装置,采用单电极放电结构,在开放的大气环境下通入氦气。采用高压窄脉冲重复频率电源激励驱动该放电装置,电源脉冲宽度约230 ns,脉冲上升沿约为120 ns。在重复频率为500 Hz的条件下,通过高速摄影初步发现放电电流脉宽约为110 ns,且无反向放电。试验结果表明:平均射流长度随电压幅值增加而增加,在一定电压幅值时射流长度有达到饱和的趋势,这是由于射流通道尾部有空气进入,电压幅值已不再是主要原因;只有在合适的气体流量值时,才能够获得较长的平均射流长度,这是由于气体流量过大或过小时射流均不足以维持形成的放电通道;此外,中心电极放电射流长度受气体流量影响较大,气体流量在一定值时可以观察到中心电极有较长的射流,射流放电强度较弱,气体流量过大或过小时中心电极几乎无放电,这是由于四周电极更易形成放电射流,削弱了中心电极放电。 ,     

纳秒脉冲电压下同轴场畸变开关多通道放电特性

使气体开关形成多通道放电是减小开关电感、通道电阻、电极熔蚀,提高开关寿命和稳定性的有效措施。设计了一种同轴场畸变气体火花开关,研究了开关在纳秒脉冲电压下的多通道放电现象。研究了脉冲电压上升速率与多通道放电特性的关系,比较了两种体积比的SF6/Ar混合气体多通道放电特性。实验结果表明:一定气压下,平均通道数随着脉冲电压上升率增加而增多,电流分布趋向均匀;相同脉冲峰值与气压比值,不同气压下,高气压下的通道数较多;SF6/Ar混合气体中,氩气含量较高情况下多通道放电特性较好。最后,结合J.C.Martin的多通道放电理论对实验结果作出了初步解释。