混合放电臭氧发生器中臭氧产生过程的传热数值模拟

为揭示混合放电臭氧高效发生的电能转换和传热机理,采用有限体积法数值求解质量、动量和能量守恒方程,实现对混合放电臭氧发生进行传热分析,并实验验证了该方法的可行性。研究结果表明:气体进入两放电间隙后温度逐渐升高,且两放电间隙温度相差较大,内放电空间平均温度比外放电空间平均温度平均高6.38 K;中心电极、内电介质、外介电质和外电极各部分内部径向温差较小;混合放电仅36.14%的电能转换为热能,其中气体从3根放电管中携带的热量分别为9.85%,7.39%和4.78%,气体经过3根放电管后最高温度仅为313.2 K。混合放电电能转化率高、气体温度相对较低,是一种非常有前途的臭氧发生形式。     

圆管型介质阻挡放电臭氧产生过程中的传热数值模拟

在介质阻挡放电臭氧产生过程中,电能大部分以热能的形式散发,且气体温度是决定臭氧产率和浓度的重要参数之一。受到研究手段和检测仪器精度的限制,关于能量转化和热量传递机理的实验研究难以开展。为此,首次采用数值模拟方法对介质阻挡放电臭氧放电室进行传热分析,并实验验证了该方法的可行性。模拟结果表明:气体温度从高压电极到玻璃介质逐渐降低,气体平均温度在短时间内快速上升后逐渐降低,而且冷却水进口温度、冷却水流量和冷却水通道宽度均对气体温度影响显著。研究结果能为气体温度的控制以及臭氧发生器的设计提供科学依据。     

平板型DBD臭氧发生多参数影响研究

DBD放电特性主要由其放电参数评定,因此研究DBD臭氧发生器的放电参数对臭氧合成实际应用具有重要意义。文中主要研究峰值电压、放电频率和气体流量的变化对平板型DBD臭氧发生器放电特性及臭氧合成特性影响。并利用Q-V Lissajous图来计算臭氧发生器等效电容、放电间隙的折合场强、放电功率等放电参数,进而得出臭氧体积分数与产率的变化关系。实验结果表明:峰值电压从5 kV增大到9 kV,放电频率从5.5 kHz上升到8 kHz时,放电功率呈线性增大,放电间隙的折合场强和介质层等效电容逐渐增加,放电间隙等效电容逐渐减小,等效总电容、放电最小电压和击穿电压基本不变;臭氧体积分数随峰值电压增大先增大后减小,随放电频率的增大缓慢上升,而臭氧产率则均减小。气体流量从0.5 L/min变化到4.5 L/min时,放电参数基本不变,臭氧产率则随之增大。放电频率一定,峰值电压较高时,气体流量适当增加能促进臭氧的生成。     

基于臭氧检测的高压开关柜初始放电预警技术

基于高压开关柜内异常放电在初始阶段会产生大量臭氧的事实,研究基于臭氧检测的高压开关柜初始放电预警技术。这一技术利用臭氧气体检测系统中的探头实时读取高压开关柜臭氧浓度,根据试验和现场测试情况设置预警值,进而对高压开关柜初始放电异常进行预警,提高电力系统运行的安全性。     

基于紫外吸收光谱检测开关柜局部放电的方法

采用紫外吸收光谱技术检测开关柜内部的臭氧气体含量,并以此判断其内部空间中是否存在局部放电现象。首先,利用放电所产生的臭氧气体对紫外光束C波段在253.7 nm波长处具有良好吸收效果的特性,以汞灯发射特定波长光信号分别测量其穿透载气、臭氧气体后的光强值;其次,依据郎伯-比尔定律计算紫外光束在吸收池的光强值、衰减值及吸收系数,进而求解臭氧气体浓度;最后,通过分析臭氧气体的浓度而判断是否存在放电现象。模拟试验和现场应用结果证明,该方法可检测到开关柜内部的臭氧气体含量,并避免环境噪声及电磁信号对检测结果的影响,直观地反映开关柜内局部放电的情况。     

空气源高频圆管型DBD臭氧产生的实验研究

电源频率和放电管长度是介质阻挡放电(DBD)臭氧产生的两个重要影响因素,在前期的研究基础上,采用合适的放电管长度和电源频率进行实验研究。实验研究了干空气源放电管长度、放电电压和气体流量对臭氧产生的影响,并进行了系统优化。研究结果表明:放电管长度由500 mm变为200 mm,在几乎不降低臭氧浓度下放电平均功率约降低了60%;臭氧浓度随放电电压和气体流量的增大先增大后降低;当流量为200 L/h、放电电压为2 698 V时,臭氧浓度与臭氧产率同时达到相对较高值,此时,臭氧浓度为5.3 g/m3时,臭氧产率为43.62 g/kWh。     

臭氧发生器研究的进展

介绍了放电式臭氧发生器电极形式、材料及电介质方面研究的新成果;讨论了近年来国内外在放电式、电解池式、紫外线辐照式臭氧发生器的新进展。分析表明提高介质的击穿强度和介电常数,改善系统散热效果,采用耐高温、耐氧化电极材料,合理设计系统结构和电极结构是提高放电式臭氧发生器性能、延长寿命的主要途径。     

放电等离子体臭氧发生技术的研究

臭氧作为解决今后环境问题的有用物质日益备受重视。为扩大臭氧在环境工作中的应用、臭氧发生技术的革新已成为当务之急，本文阐述了放电等离子体臭氧发生技术的研究现状及进展。     

沿面放电生成臭氧的传输损耗研究EI北大核心CSCD

臭氧以其强氧化性得到了广泛应用,而实际应用过程中臭氧的传输损耗大大降低了其利用效率。鉴于此,采用沿面放电等离子体产生臭氧,研究了臭氧在传输过程中传输距离、臭氧初始质量浓度、气体流速、气体相对湿度和气体温度等因素对臭氧的衰减影响。实验结果表明,传输距离、气体相对湿度、气体温度的升高以及气体流速的降低均会加速传输过程中臭氧的损耗。此外,在该实验的条件下,臭氧质量浓度范围在62.86~124.60 mg/m3时,对衰减率的影响不大,保持在15%左右。     

沿面放电生成臭氧的传输损耗研究

臭氧以其强氧化性得到了广泛应用,而实际应用过程中臭氧的传输损耗大大降低了其利用效率。鉴于此,采用沿面放电等离子体产生臭氧,研究了臭氧在传输过程中传输距离、臭氧初始质量浓度、气体流速、气体相对湿度和气体温度等因素对臭氧的衰减影响。实验结果表明,传输距离、气体相对湿度、气体温度的升高以及气体流速的降低均会加速传输过程中臭氧的损耗。此外,在该实验的条件下,臭氧质量浓度范围在62.86~124.60 mg/m3时,对衰减率的影响不大,保持在15%左右。     

提高臭氧发生器放电室效率的研究

本文根据管式臭氧发生器放电室的电晕放电功率方程式,分析了臭氧发生器的发展趋势,设计了搪瓷介电体的臭氧发生室。对玻璃和搪瓷材料进行了电性能参数测试。对玻璃和搪瓷民体的臭氧发生器产率和电耗参数进行了测量比较。结果表明：Ｘ 搪瓷介电体臭氧发生器比玻璃介电体臭氧发生器臭氧产率提高了４４％,电耗降低了４２％。     

用气相沿面放电生成臭氧方式降解偶氮染料废水的影响因素分析

为提高臭氧降解和脱色染料废水的效果,通过沿面放电臭氧生成-废水处理一体化反应器降解偶氮染料废水研究了供电电源类型、放电电压、放电反应器内注入的气体组分及流量、废水电导率、催化剂等因素对染料降解的影响。研究结果表明:同50Hz工频电源相比,在相同的输入功率下,高频电源降解偶氮染料效果更快;沿面放电反应器内注入的气体成分影响染料降解率,注入氧气时,甲基红降解率最高,注入氮气时,甲基红几乎没有降解;注入气体流量影响气相和液相臭氧浓度及染料废水的湍流度,进而影响甲基红的降解率;废水电导率对甲基红降解影响不大;二氧化钛添加量影响甲基红的降解,染料降解初期,适量的二氧化钛有利于甲基红的降解。     

电气设备状态监测与故障诊断技术的现状与展望

介绍电气设备监测与诊断技术的意义和监测诊断系统的组成，阐述了几种设备的监测诊断技术。对变压器，主要介绍局部放电和油中溶解气体监测；对电容式设备，主要介绍介质损耗因数、电容量及三相不平衡电流监测；对金属氧化物避雷器，主要介绍阻性电流监测。监测诊断技术的发展趋势是：加强信号处理、识别诊断、人工智能等新技术的应用；综合性、分布式、远程监测与诊断系统和电力设备虚拟医院的研发；以可靠性为中心的维修策略的研究及推广等。     

Production of ozone by surface and glow discharge at cryogenictemperatures

The generation of ozone at cryogenic temperatures is investigated with a special interest in increasing the yield of ozone by using low temperatures of liquid natural gas. Two modes of plasma chemical processes are studied, both based on electric discharges: one is the high-frequency surface discharge mode under ordinary gas pressure and at a temperature above the liquid temperature of ozone at this pressure (-111°C); the other is the glow discharge mode under a low gas pressure (0.5-2.0 torr) and low gas temperature (-190°C). The surface discharge mode uses a novel ozonizer developed by the authors made of 92% high-purity alumina and tungsten electrodes sintered together. This ozonizer has an extremely high resistance to large temperature gradients and thermal shock, which is a prerequisite for cryogenic operation. The glow discharge mode uses a Pyrex glow tube with a separate liquid-ozone collector. A dramatic improvement in the energy yield of ozone generation is achieved in both modes of cryogenic operation. The results of preliminary test for cryogenic ozone generation are very encouraging     

电晕放电自由基簇射反应器中臭氧的生成

从电极气条件变化着手,对放电过程以及NO脱除过程中自由基簇射反应器内臭氧的生成进行了较为深入的分析。研究结果表明:(1)在相同的放电功率下,当电极气为氧气时产生的臭氧最多,通入空气时其次,而不通电极气时最少;(2)随着电极气湿度的增加,臭氧的产生量逐渐减少;(3)电极气流量的增加提高了臭氧的产生量,但考虑经济性,电极气流量有一最佳值;(4)在NOx脱除过程中,自由基簇射反应器内臭氧浓度大大减少,且随着烟气中NO浓度的增加,臭氧浓度逐渐减少,认为其主要原因是臭氧和氧自由基参与了NO的氧化过程。     

Hydrogen peroxide and ozone formation in hybrid gas-liquid electrical discharge Reactors

Ozone in the gas phase and hydrogen peroxide in the liquid phase were simultaneously formed in hybrid electrical discharge reactors, known as the hybrid-series and hybrid-parallel reactors, which utilize both gas phase nonthermal plasma formed above the water surface and direct liquid phase corona-like discharge in the water. In the series configuration the high voltage needle-point electrode is submerged and the ground electrode is placed in the gas phase above the water surface. The parallel configuration employs a high voltage electrode in the gas phase and a high voltage needle-point electrode in the liquid phase with the ground electrode placed at the gas-liquid interface. In both hybrid reactors the gas phase concentration of ozone reached a power-dependent steady state, whereas the hybrid-parallel reactor produced a substantially larger amount of ozone than the hybrid series. Hydrogen peroxide was produced in both hybrid reactors at a similar rate to that of a single-phase liquid electrical discharge reactor. The resulting concentration of H/sub 2/O/sub 2/ in the hybrid reactors, however, depended on the pH of the solution and the gas phase ozone concentration since H/sub 2/O/sub 2/ was decomposed by dissolved ozone at high pH.     

沿面/体介质阻挡放电装置的放电及臭氧生成特性

相对于体介质阻挡放电(VDBD),沿面介质阻挡放电(SDBD)等离子体可以更高效地生成反应活性物质,在气体处理方面显示了较高的效率。但沿面放电仅沿介质表面发展,限制了放电等离子体装置处理气体的能力。文中设计了一种新型的沿面/体复合DBD装置,通过在垂直于沿面放电高压电极的上部增加体放电电极,用于扩展等离子体的空间分布并提高活性物质的产量,研究了电极构型、放电气隙、放电电压及气体体积流量等对装置的放电特性及臭氧生成的影响。在空气间隙为4.5mm,外加电压幅值为16kV时,SDBD放电功率为11.2W,VDBD放电功率为4.6 W,复合装置的放电功率为19.7 W;分别测量复合装置中的沿面放电和体放电功率发现,复合装置的沿面放电功较单一沿面放电装置的放电功率提高了1.1倍,而复合装置的体放电功率较单一体放电功率提高了1.9倍。臭氧测试结果表明,复合装置生成的臭氧质量浓度可达3.0 mg/L,分别是SDBD和VDBD的3.8倍和5.0倍。     

Superposed effect of UV rays on ozone generation by electrical discharge

Generally, ozone is generated by using silent discharge or surface discharge; however, the energy efficiency of ozone generation by using only one kind of discharge is about 200 g/kWh. The energy efficiency of ozone generation is about one-fifth of the theoretical energy efficiency. Ozone decomposition occurs at high concentrations, high temperatures, and so on. In order to increase ozone generation efficiency, many studies of ozone generation methods have been carried out to date. Experiments on ozone generation by using surface discharge and UV rays were carried out. In an experiment on superposing surface discharge and UV rays in the same space, the ozone yield by the superposing mode is lower than either the ozone yield by surface discharge or by UV rays at the same power. It appears that noticeable ozone dissociation by UV rays occurs because a high ozone concentration is achieved by the superposing mode. In cascade connection of a surface discharge reactor and UV lamp reactor, the ozone yield of the cascade mode (from the UV lamp reactor to the surface discharge reactor) is higher than that of the superposing mode at the same power. It is confirmed that cumulative disassociation is an effective reaction of ozone generation. © 1998 Scripta Technica, Electr Eng Jpn, 123(4): 8–14, 1998     

Improvement of the energy efficiency in the decomposition of dilute trichloroethylene by the barrier discharge plasma process

In order to improve the energy efficiency in the dilute trichloroethylene (TCE) removal by the nonthermal plasma process, the barrier discharge reactor was studied experimentally. It is investigated by combining it with catalyst of manganese dioxide at the downstream of the barrier discharge reactor. Decomposition efficiency by the barrier discharge reactor was about 83% at the gas flow rate 2 L/min, where the dilute TCE concentration is 250 ppm. Decomposition efficiency with passing through manganese dioxide was improved about 99% at the specific energy of 40 J/L. However, other by-products including ozone and oxidation by-products such as DCAC and TCAA were detected by the gas chromatograph mass spectrometry or the Fourier transform infrared spectroscope measurement. DCAC is generated at the plasma reactor, but TCAA is generated at catalyst during ozone decomposition. CO/sub x/ yield increased about twice with passing through catalyst in the Direct Process. Nitric oxides such as NO, NO/sub 2/, and N/sub 2/O did not generate so much in this barrier discharge process. The dielectric barrier discharge process combined with manganese dioxide is considered as a very desirable way to improve the energy efficiency.