直流大气压辉光放电高能电子密度的空间分布

利用针阴极和水阳极,在6 mm的空气隙产生了大气压空气辉光放电。该大气压辉光放电具有明显的负辉区、正柱区和阳极辉区等明亮的发光区。通过研究放电的电压电流特性,发现该放电处于亚辉光放电到正常辉光放电阶段。由于氮分子第二正带系337.1 nm的光谱强度反映高能电子密度,对337.1 nm谱线的强度进行了空间分辨测量。结果发现高能电子在针尖附近密度最大,而其他区域相差不多。随电压升高,高能电子密度减少。增大限流电阻,高能电子密度也减少。氧原子对杀菌消毒具有重要作用,利用发射光谱法对氧原子谱线强度的空间分布进行了测量,发现氧原子谱线强度与高能电子的空间分布及其随参数的变化关系一致。     

发射光谱研究多针对板电晕放电O活性原子特性

利用发射光谱技术在大气压下测量了空气中多针对板负直流电晕放电和正电晕流光放电产生的O(3p5 P→3s 5 S02777.4nm)活性原子发射光谱。在负电晕放电中,研究了放电功率、电极间距、N2含量和相对湿度等因素对O活性原子产生过程的影响;在正电晕流光放电阶段,研究了O活性原子相对密度在放电反应空间的分布特点。结果表明:O活性原子产量随放电功率的增加而增大,随电极间距增大而减少,随相对湿度和氮气含量的增加,其产量先增大后减少;O活性原子相对密度沿针尖轴向呈先增大后减小的趋势。     

脉冲放电脱硫反应器中高能电子密度分布的光谱研究

脉冲流光放电产生的大于等于11.2 eV的高能电子能将处于基态的氮分子激发到N₂(C3Π_u)态,测试脉冲流光放电时的N₂(C3Π_u→B3Πg)发射光谱相对强度可以得出脉冲流光放电产生的高能电子的密度。实验在室温常压下研究了空气中线-板式脉冲流光放电脱硫反应器内高能电子密度分布情况,并研究了脉冲电压、反应器的线线间距对反应器内高能电子密度分布的影响。实验结果表明,反应器内的高能电子主要集中在放电线附近高电场区内,随着离放电线的距离增大,高能电子密度减小;脉冲电压对高能电子密度有很大影响,随着电压的升高,高能电子密度基本呈线性增大;线板间距固定,线线间距为线板间距的0.6～1倍时,反应器内高能电子密度分布较为均匀。     

微隙介质阻挡放电装置中的空气均匀放电光谱特性

大气压空气中介质阻挡均匀放电产生的等离子体在工业领域具有广阔的应用前景,为研究其产生条件及机理,利用微间隙介质阻挡放电装置,在大气压空气中实现了均匀放电。电学实验结果表明,低电压时电流波形在电压每半个周期存在若干个脉冲宽度很小的脉冲,肉眼观察到大量的微放电丝,随着外加电压增加,放电功率逐渐增加,放电空间内微放细丝增多。当电压增大到9.2 kV时,电流波形在电压每半个周期只存在一个宽度较大(约5.5 μs)强度较强的脉冲,观察不到微放电丝,微放电最终扩展叠加形成均匀放电。采集了光谱范围为330～420 nm的发射光谱,氮分子第二正带系337.1 nm的谱线强度明显比氮分子离子第一负带系391.4 nm的强。将337.1 nm谱线的强度归一,391.4 nm谱线的强度即反应了电子平均能量的大小,同时拟合计算了反映分子内部能量的氮分子振动温度。结果表明电子平均能量和分子内部能量都随外加电压的增加而降低。表明放电空间电场能量较低时不容易形成丝状放电,均匀放电模式中电子平均能量比微放电丝放电模式中的低。这些结果对于空气中介质阻挡均匀放电在工业应用方面具有一定的指导意义。     

狭缝微放电等离子体参数的光谱测量

利用平行管水电极介质阻挡放电装置,在氩气和空气混合气体中,得到了狭缝微放电等离子体。利用发射光谱法,研究了此放电中分子振动温度、分子转动温度和电子的平均能量随气体压强的变化。通过氮分子第二正带系(C3Πu→B3Πg)的发射谱线计算了氮分子的振动温度;利用氮分子离子(N2+)的第一负带系(B2Σu+→X2Σg+)的发射谱线计算了氮分子的转动温度;测量了氮分子离子391.4 nm和激发态的氮分子337.1 nm两条发射谱线的相对强度之比,研究了电子能量的变化。结果表明,当压强从60 kPa增大到100kPa,分子振动温度及分子转动温度均减小,氮分子离子谱线与激发态的氮分子谱线的强度之比亦减小。     

直流激励等离子体喷枪的发光特性研究

利用针-板喷枪装置,在直流电压激励下产生了大气压非平衡态低温等离子体羽。采用光学方法,研究发现等离子体羽的放电模式为脉冲放电。通过比较放电的总发光信号、337.1 nm谱线的发光信号与电流信号,发现电流信号脉冲宽度最大,337.1 nm谱线的信号脉冲宽度最小。通过对发光信号频率随电压的变化关系进行研究,发现放电脉冲频率随电压的增大而增大。利用光谱仪测量了337.1 nm的谱线强度,发现它随气流增大减小,随电压增大表现为先增大后减小。利用气体放电理论,对以上物理现象进行了定性解释。这些研究结果对于大气压非平衡态低温等离子体羽的产生和应用都具有重要意义。     

发射光谱研究多针对板正电晕放电形貌

利用光学发射光谱(OES)法检测N₂发射光谱,研究了常压下多针对板正电晕放电中辉光放电和击穿流光放电的高能电子分布,并与相同电极结构下负电晕放电进行了比较。根据N₂第二正态激发谱峰I_SPB在空间的分布,较精确地确定了辉光放电电离区形貌和击穿流光放电电通道形貌,体积分辉光放电中I_SPB获知I_SPB与放电电流I之间的关系。辉光放电中,电离区范围和I_SPB比负电晕放电小,电子雪崩沿针径向比沿轴向发展范围大;随着U升高,电离区范围只沿针轴向小幅度增大;I_SPB的积分值与I近似成二阶线性关系。击穿流光放电中,针板之间形成放电通道;针尖周围I_SPB较强的区域成“子弹状”,距离针尖较远的放电通道内高能电子密度沿针轴向分布比较均匀,沿针径向先略有增大后减小。     

单针电极放电的发光特性

采用单针电极放电装置在氩气中产生了稳定的均匀等离子体。利用光学方法对单针放电特性进行了研究,结果表明单针放电等离子体的长度随外加电压峰值、气压的增大而增大,随空气含量的增大而减小。利用光电倍增管对单针电极放电等离子体羽的发光信号进行了空间分辨测量,发现靠近单针电极的羽头和等离子体羽其余部分放电行为不同。其中羽头源于针尖附近的电晕放电,它仅在外加电压负半周期的发光较强,正半周期发光几乎探测不到。而等离子体羽其余部分的放电在外加电压正、负半周期均存在,且正半周期强于负半周期。研究表明,外加电压正半周期的等离子体羽是源于发光光层(等离子体子弹)的传播,而负半周期等离子体羽的不同位置几乎同时放电。     

半球形电极弥散放电等离子体参量的光谱研究

利用两个半球形水电极介质阻挡放电装置,在空气中实现了弥散放电,采用发射光谱法,对分子振动温度、分子转动温度及电子平均能量等随电压的变化进行了研究。实验利用氮分子第二正带系(C3Πu→B3Πg)的发射谱线得到了氮分子的振动温度;通过氮分子离子(N2+)的第一负带系(B2Σu+→X2Σg+)的发射谱线计算了氮分子的转动温度;采集了氮分子离子391.4nm和激发态的氮分子337.1nm两条发射谱线的相对强度之比,研究了电子的平均能量的变化。结果表明:随外加电压的增加,分子的转动温度呈上升趋势,分子的振动温度呈下降趋势,电子能量呈缓慢的下降趋势。     

光谱法研究低气压空气介质阻挡放电均匀性

利用介质阻挡放电装置.在低气压空气中得到了均匀放电,并采用光谱法,研究了放电等离子体温度的空间均匀性.实验采集了氮分子光谱,采用氮分子第二正带系C3Ⅱu→B3Ⅱg计算振动温度;采用氮分子离子第一负带系计算转动温度(气体温度).实验发现,振动温度随电压增加而减小,而转动温度随电压增加而增大.等离子体振动温度和转动温度在空...     

Simulation and Experimental Study for Degradation of Organic Dyes Using Dual pin‐to‐plate Corona Discharge Plasma reactors for Industrial Wastewater Treatment

This work researches the possibility of increasing the dye removal efficiency from wastewater using nonthermal plasma. A study for the optimal air gap distance between dual pin and surface of Acid Blue 25 dye solution and thickness of ground plate is carried out using 3D‐EM simulator to find maximum electric field intensity at the tip of both pins. The consequences display that the best gap for corona discharge is approximately 5 mm using 15 kV source. In addition, the optimum plate thickness is 0.1 mm. These distance and thickness were mentioned are constant during the study of other factors. Dual pin‐to‐plate high‐voltage corona discharge plasma system is presented to investigation experimentally the gap distance, thickness of ground plate, initial dye concentration, pH solution and conductivity on the amount of Acid Blue 25 dye color removal efficiency from wastewater. There is a large consensus among the simulation and experimental work in the air gap and thickness of ground plate. Where the decolorization for air gap 5 mm is 95.74 at time 35 min compared with 91% and 17% for 1 mm and 20 mm gap distance respectively. Also, the discharge energy at each air gap are calculated. Measurement results for the impact of thickness of an Aluminum ground plate on color removal competence showed color removal efficiencies of 86.3%, 90.78% and 98.06%, after treatment time 15 min for thicknesses of 2, 0.5 and 0.1 mm respectively. The decolorization behavior utilizing dual pin‐to‐plate corona discharge plasma system display 82% pigment evacuation proficiency inside 11min. The complete decolorization was accomplished within 28min for distinctive examined introductory color focuses 5 ppm up to 100 ppm. Likewise, the impacts of conductivity by utilizing diverse salts as AlCl3, CaCl2, KCl and NaCl and with distinctive focuses have been explored. The rising of the solution conductivity leads to the reduction of decolorization efficiency. The decolorization efficiency and discharge energy are calculated at different concentration molarity for AlCl3, CaCl2, KCl and NaCl. It was observed that the presence of salts at the same concentration level substantially decreased the rate and the extent of decolorization. The results indicate that the optimum pH for the decolorization of Acid Blue 25 dye is in the range between 3 and 6. Furthermore the conductivity and discharge energy were measurement at each value of pH. Energy yield for decolorization and Electrical Energy per Order (EE/O) under different initial pH value were calculated. A kinetic model is used to define the performance of corona discharge system under different value of pH. The model of pseudo ‐zero, pseudo‐first order, and pseudo‐second order reactions kinetic are utilized to investigate the decolorization of Acid Blue 25 dye. The rate of degradation of Acid Blue 25 dye follows the pseudo‐first order kinetics in the dye concentration. Energy consumption requirements for decolorization was considered. The outcomes will be useful for designing the plasma treatment systems suitable for industrial wastewaters. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

空心针-板电极大气压氩气辉光放电的特性研究

大气压均匀放电等离子体在工业领域具有非常广泛的应用前景,它是利用直流电源激励的空心针-板放电装置,以氩气为工作气体在大气压空气中产生均匀稳定的放电。对氩气流量和气隙间距对辉光放电发光特性的关系进行了研究,结果表明放电所产生的等离子体柱连接两个电极,发光较为均匀(观察不到放电丝)。在板电极附近放电等离子体柱直径最大,最大直径随着电流和气流的增大而增大。放电伏安特性研究发现,与低气压辉光放电相类似,两电极间的电压随着电流的增大而减小,并且随气流和气隙间距的增大而增大。对该大气压直流均匀放电在扫描范围为330～450 nm的光学发射光谱进行分析,获得了放电等离子体的分子振动温度和谱线强度比I_391.4/I_337.1随氩气流量和气隙间距的变化关系。I_391.4/I_337.1均随流量和气隙间距的增大而降低。对等离子体柱的I_391.4/I_337.1沿气流方向(等离子体柱轴向)进行了空间分辨测量,并进行了定性分析,结果表明,振动温度及电子平均能量随着远离空心针口距离的增大而增大。这些结果对大气压辉光放电在工业中的应用具有重要意义。     

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.     

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。     

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.     

直流激励的大气压氩气喷枪的光谱研究

利用正高压驱动空心针-板喷枪装置,通入工作气体氩气,在大气压空气中产生了均匀稳定的喇叭状等离子体羽。电学和光学测量结果表明,放电虽然是在直流电源驱动下工作,但放电为周期性的脉冲。通过对等离子体羽发光信号进行空间分辨测量,研究了脉冲的形成机理,发现除针尖附近的电晕放电外,等离子体羽是以正流光(等离子体子弹)从针尖向着接地电极方向传播的。采用光谱学方法,对电子激发温度随电压的变化及其空间分布进行了测量。结果表明,电子激发温度(约为3 eV)随电压的增大而升高,在一定电压下,电子激发温度沿气流方向也在升高。     

纳秒脉冲空气辉光放电等离子体及应用

采用基于半导体断路开关的纳秒脉冲高压电源,在两个金属电极之间产生放电区间为1 600mm×100 mm×25 mm的常压辉光空气等离子体。等离子体发生器采用负高压针电极阵列与平板阳极结构,针电极的直径为1 mm,长度为20 mm,针电极之间的间隔为20 mm,针电极与平板零电位之间的距离为25mm,在每个负高压针电极末端周围同时形成圆锥形辉光放电,在平板地电极则形成大面积辉光放电。采用电压探针测量了该新型等离子体的放电特性,结果表明:放电脉冲的上升时间为26 ns,最高脉冲输出峰值电压为27 kV;利用该辉光等离子体对幅宽为1 000 mm聚四氟乙烯薄膜进行了表面改性处理,处理后其表面接触角由原来的124°降到69°,亲水性能大为提高。     

固态阴极射线器件复合加速层的研究

固态阴极射线器件的加速层,是提高固态阴极射线性能的重要部分,它能够加大电子能量,倍增电子数量。其中增加注入电子从而提高过热电子的数量,是提高固态阴极射线器件性能的关键。为此 ,文章尝试将加速层复合,兼顾加速与电子注入性能。首先将SiO₂,ZnS和ZnO分别与有机聚合物MEH-PPV组合,确定较适合的复合加速层的组合：SiO₂/ZnS和 ZnO/SiO₂。然后将这两种复合加速层的性能对比,发现SiO₂/ZnS的性能更优越,因为电子注入性能ZnS和ZnO相当,而电子加速倍增性能ZnS明显优于ZnO,其中 SiO₂为主要的加速层,而ZnS起到降低注入势垒变成阶梯势垒的作用。最后又将复合加速层结构的固态阴极射线器件和传统的SiO₂夹层固态阴极射线器件对比,发现这种复合 加速层结构,尤其在高场下,可提高固态阴极射线的初电子源和过热电子的数目,从而提高其发光效率具有促进作用。