电荷电压法测量DBD等离子体的放电参量

在DBD应用研究中，使用电荷电压法能够测量许多重要参量，如放电功率、放电间隙等效电容、电介质层等效电容、着火电压、放电间隙等效电压及放电间隙电场强度等．同时根据电荷电压图形随工作条件及状态变化的情况还可以诊断DBD等离子体的工作稳定性．文章对相关原理、模拟实验结果及实际应用效果进行了介绍．     

同轴介质阻挡放电中活性粒子的光谱检测

同轴介质阻挡放电具有广泛的应用前景。采用光学方法,利用水电极介质阻挡放电装置,对空气同轴介质阻挡放电特性及活性粒子光谱强度进行了研究。光谱测量结果发现放电发射谱中存在777.5和844.6nm的氧原子谱线,表明等离子体中产生了高化学活性的氧原子。测量了放电中氧原子谱线强度随物理参数(外加电压、流量和含量)的变化关系。结果发现氧原子谱线强度随着外加电压的增加而增强;随着流量或氩气含量(空气中混入少量氩气)的增加,谱线强度先增大后减小,当流量为30L.min-1或者氩气含量为16.7%时氧原子谱线强度达到最大值。     

介质势垒放电(DBD)等离子体中NO荧光发射谱研究

利用介质阻挡放电 (DBD)等离子体技术对大气污染物NO分子进行了光谱研究 ,得到了低气压条件下放电等离子体在 2 1 0～ 2 80nm光谱范围内的荧光发射谱。该谱明显的表现为双峰结构 ,谱线均成对出现 ,强度分布符合Frank Condon原理 ,且最大峰值位置出现在 2 36nm处 ,将该组谱线归属为NO分子的A2 ΣA →X2 Π1 / 2 ,2 / 3 跃迁。荧光产生过程为 :基态NO分子与高能电子发生非弹性碰撞被激发至激发态A2 Σ 后自发跃迁回基态同时辐射出荧光。通过测量等离子体中NO分子和N2 分子 337nm谱线强度随时间的变化关系 ,初步证实了放电等离子体中存在的NO分子的分解机制为 :e NO→N O e,N NO→N2 O ,O NO→NO2 hν。     

同轴枪放电等离子体电流片的运动特性研究

同轴枪放电可以产生高速度、高密度的等离子体射流,在天体物理、核物理等研究领域具有广泛的应用.基于同轴枪放电等离子体运动的"雪犁模型"分析,本实验通过对等离子体光电信号和磁信号的测量及放电照片的拍摄,研究了不同放电电流和气压对同轴枪放电等离子体电流片的运动特性、电流通道分布的影响.实验结果发现:一次放电过程中,气压为10 Pa、放电电流为35.7—69.8 kA时,随着放电电流的增加,等离子体喷射速度增加,输运距离与离子携带的轴向动能成正比,大电流条件下,等离子体喷出枪口时易于在枪底端形成新的电流通道;气压为5—40 Pa、放电电流为49.8 kA时,随着气压的增加,等离子体喷射速度减小,输运距离缩短,高气压下,等离子体喷出枪口时在枪底端未产生新的放电通道,这与放电过程中遗留在枪底端的带电粒子和电流片渗漏残留在枪内的中性粒子共同形成的阻抗通道有关;电流反向时,二次放电击穿位置发生在电极头部,放电过程中存在多次放电现象.     

介质阻挡放电分解甲醇发射光谱分析

利用光学多道分析系统（Optical Multiple Analysis -OMA）,采用发射光谱方法,对甲醇气体介质阻挡放电 (dielectric barrier discharge---DBD)分解制氢过程进行了实验研究.通过对甲醇气体DBD放电等离子体荧光光谱的归属,确定了甲醇放电的主要荧光产物为CO、OH、H和CH;另外,还对CO和Ｈａ的荧光辐射强度随放电时间的演变过程进行了实验研究,发现在放电初始阶段,CO和Ｈａ的荧光辐射强度随放电时间急剧增强,表明了DBD放电能有效地分解甲醇气体,并由此对甲醇分解过程进行了分析讨论.在放电等离子体甲醇制氢过程中,最终产物是H2和CO;H2主要来自于ＣＨ２Ｏ分解以及甲醇分解产生的H原子直接生成;CO主要来源于ＣＨ２Ｏ分子分解产生.ＣＨ２Ｏ是甲醇分解制氢过程中一个关键的中间产物.     

基于Kriging代理模型的DBD等离子体控制叶顶泄漏流动研究

本文采用数值方法研究了布置于涡轮动叶叶顶的多个等离子体激励器组合对间隙泄漏流动的影响。结果表明:不同的极板数目和位置组合对间隙泄漏流量有着十分明显的影响。在叶顶沿吸力边布置等离子体激励器的最佳位置在大约55%S/Sps处,布置相同数目的等离子体激励器,在靠近尾缘处的控制效果要远好于在前缘附近的控制效果;等离子体激励器在叶顶靠近吸力边处产生诱导涡,阻碍了间隙内流体的流动,使泄漏流体的速度降低。同时还会使得分离泡的破碎提前,有利于减小掺混损失;对泄漏流动的控制效果不会随着等离子体极板数增加而持续增强,而存在一定限度,最优布置方式的泄漏流量较原型下降约46%,相应的出口截面能量损失下降了15.7%。     

DBD在原子光谱领域内的应用进展

介质阻挡放电因其体积小、结构简单、能耗低、工作温度低、样品解离/激发能力强等显著特点,特别适合于分析仪器的微型化和便携化。目前,基于介质阻挡放电的原子化器或激发光源已成功应用于原子吸收光谱仪、原子荧光光谱仪和原子发射光谱仪中,促进了小型化原子光谱仪器的发展。总结了介质阻挡放电技术在原子光谱领域内的研究进展,着重阐述了介质阻挡放电-原子发射光谱系统在不同进样方式下的应用情况,分析了每种进样方式的优缺点。本文还对介质阻挡放电技术在诱导蒸气发生、固体直接进样方面的新应用方向进行了评述。虽然介质阻挡放电技术已在原子光谱领域内得到广泛的应用,但其反应机理仍然不明确,制约了其后续的拓展研究。     

同轴波纹返波管色散特性研究及粒子模拟

计算了同轴波纹慢波结构的色散特性,分析了波纹周期长度、波纹幅值大小以及同轴内导体半径对慢波结构色散特性的影响。研究表明内导体的存在使系统截止频率升高,系统尺寸可比普通波纹波导慢波系统更大, 并且可以采用大半径电子注并工作在低磁场状态。运用Magic软件对同轴波纹返波管进行了数值模拟, 发现同轴波导内场分布有利于注波互作用,在数值模拟基础上设计出高效率、低磁场的非均匀同轴波纹返波管,互作用效率达60%,聚束磁场小于1 T。     

液固DBD等离子体煤液化反应动力学分析

本文从DBD液固表面等离子体鞘层的研究出发,通过建立流体力学方程组来确定鞘层内的电子浓度,进而确定电子温度;借助碰撞理论和Boltzmann方程,给出反应速率常数随电子温度变化曲线.该曲线与实验曲线相吻合,从而说明等离子体鞘层理论和速率常数作为分析DBD等离子体煤液化反应机理方法的可行性和合理性,为分析、预测反应进程和反应产物提供理论依据.     

同轴波纹返波管色散特性研究及粒子模拟

 计算了同轴波纹慢波结构的色散特性,分析了波纹周期长度、波纹幅值大小以及同轴内导体半径对慢波结构色散特性的影响。研究表明内导体的存在使系统截止频率升高,系统尺寸可比普通波纹波导慢波系统更大, 并且可以采用大半径电子注并工作在低磁场状态。运用Magic软件对同轴波纹返波管进行了数值模拟, 发现同轴波导内场分布有利于注波互作用,在数值模拟基础上设计出高效率、低磁场的非均匀同轴波纹返波管,互作用效率达60%,聚束磁场小于1 T。     

Study of ozone generation in an atmospheric dielectric barrier discharge reactor

Ozone (O₃) generation in a dielectric barrier discharge (DBD) reactor driven by a pulsed power supply was investigated at atmospheric pressure and room temperature. An O₃ generation efficiency model is established in which discharge power, O₂ concentration, gas flow rate, and volume of the discharge space are included. Constants in the O₃ generation efficiency model were obtained by fitting the model with experiment results. O₃ concentration can be simply calculated from the energy density and initial O₂ concentration. Comparison on O₃ concentrations from calculation with references is given.     

Effects of dielectric barrier discharge plasma on pathogen inactivation and the physicochemical and sensory characteristics of pork loin

This study aimed to evaluate the use of a dielectric barrier discharge (DBD) plasma system to improve the safety of pork loins. When pork loin was exposed to DBD plasma with the input gases He and He + O₂, the population of Escherichia coli was reduced by 0.26 and 0.50 log cycles following a 5-min treatment and by 0.34 and 0.55 log units following a 10-min treatment, respectively. That of Listeria monocytogenes was also reduced from 0.17 to 0.35 and 0.43 to 0.59 log cycles when the samples were exposed to DBD for 5 and 10 min using He and He + O₂, respectively. The pH and L*-values (lightness) of the samples decreased significantly with DBD plasma treatment, but a*- (redness) and b*-values (yellowness) exhibited no obvious changes. Lipid oxidation, measured by TBARS values, was greater in samples with He + O₂ than in other samples. Significant reductions in sensory quality parameters (appearance, color, odor, acceptability, etc.) were observed in DBD-treated samples. These results indicate that the DBD plasma system has potential for use in sanitizing pork loins by inactivation of foodborne pathogens, although the effect was limited. In order to meet market requirements, however, a method to overcome sensory deterioration of pork loins should be developed and applied.     

Surface wettability of atmospheric dielectric barrier discharge processed Armos fibers

Wettability of Armos fibers has been investigated after exposed to dielectric barrier discharge (DBD) plasma, which was performed at atmospheric pressure in air while varying the sample treatment time between 9 and 27 s. Contact angles and surface free energy of the original and plasma-treated fibers were measured with dynamic contact angle analysis (DCAA) to reveal the correlation between the fiber wettability and the surface treatment, including surface composition and topography modifications, which were evaluated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. It was found by XPS analysis that the O/C atomic ratio on Armos fiber surface can be increased from 0.134 to 0.248 after the 18 s exposure to the plasma and many polar functional groups were proved to be incorporated into the surface, which aided good wetting. In addition, AFM observations revealed the changes of fiber surface microstructure, showing significant enhancement of the surface roughness after the treatment, which could also bring the fiber better wettability. What's more, the impacts of fiber surface treatment on its tensile properties were characterized by single fiber tensile strength (SFTS) testing. Results showed that Armos fibers exhibited only slight reductions in their tensile strengths with the great enhancement in fiber surface free energy.     

Effects of air dielectric barrier discharge plasma treatment time on surface properties of PBO fiber

In this paper, the effects of air dielectric barrier discharge (DBD) plasma treatment time on surface properties of poly(p-phenylene benzobisoxazole) (PBO) fiber were investigated. The surface characteristics of PBO fiber before and after the plasma treatments were analyzed by dynamic contact angle (DCA) analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). DCA measurements indicated that the surface wettability of PBO fiber was improved significantly by increasing the fiber surface free energy via air DBD plasma treatments. The results were confirmed by the improvement of adhesion of a kind of thermoplastic resin to PBO fiber which was observed by SEM, showing that more resin was adhering evenly to the fiber surface. AFM measurement revealed that the surface topography of PBO fiber became more complicated and the surface roughness was greatly enhanced after the plasma treatments, and XPS analysis showed that some new polar groups (e.g. OCO) were introduced on plasma treated PBO fiber surface. The results of this study also showed that the surface properties of PBO fiber changed with the elongation of plasma treatment time.     

Coaxial rf atmospheric pressure dielectric barrier air-helium plasma characteristics

The electrical and optical characteristics of a coaxial rf atmospheric pressure dielectric barrier discharge (DBD) with one electrode covered with glass and with helium in air were investigated. Optical measurements with an intensified charge coupled device (ICCD) camera combined with the voltage and power vs. current data provided identification of the α to γ mode transitions. The coaxial design allowed operation with very low power density plasmas (0.18 W/cm³) and a much larger plasma size (13 mm) than the parallel plate designs.     

共面介质阻挡放电特性研究

对共面介质阻挡放电(DBD)的放电过程进行了实验和理论研究. 在实验中设计了分段电极方法来获取放电过程中不同位置上的局域电流和光辐射特性，得到了阴极上等离子体的扩展速度，并与二维流体数值模拟结果进行了比较. 结果表明，在共面DBD的暂态放电过程中，电极上空等离子体区域始终存在有不均匀电场，导致了不同位置上放电电流和光辐射分布的不一致. 同时研究还表明，在DBD放电过程中应当考虑表面光致二次电子发射. 关键词： 介质阻挡放电 分段电极 放电特性     

大气压氩气介质阻挡辉光放电的一维仿真研究

为了研究氩气(Ar)中介质阻挡大气压辉光放电(APGD)的放电机理, 通过建立一个一维的多粒子自洽耦合流体模型, 采用有限元方法进行数值计算, 得到了气体间隙压降、介质表面电荷密度、放电电流密度随时间的周期变化波形, 以及电子、离子、亚稳态粒子密度和空间电场强度的时空分布. 仿真计算结果表明：介质表面积聚的电荷对于放电的过程的起始及熄灭具有重要作用;当增大外施电压时, 放电击穿时刻提前, 放电电流密度和介质表面电荷密度峰值增大, 表明放电过程更加剧烈;随着阻挡介质相对介电常数的增大, 放电电流密度也随之增大. 各粒子密度及电场的时空分布表明放电过程在外施电压半个周期中只有一次放电, 且存在明显的阴极位降区、负辉区、等离子体正柱区等辉光放电的典型区域, 为大气压辉光放电(APGD).     

The role of vibrational temperature variations in a pulsed dielectric barrier discharge plasma device

The use of dielectric barrier discharge (DBD) plasmas has become a practical way to carry out surface treatment where precise control of the plasma parameters, such as rotational and vibrational temperatures (T_rot and T_vib), is required. As the T_vib of an atmospheric pressure plasma jet appears to be the most important parameter related to the improvement of surface treatments, in this work, we analysed two methods to increase the values of T_vib in a DBD plasma jet device. One of the methods is to reduce the exit size (ø) of the DBD reactor, which results in an increase in the measured T_vib values, due to an increase in the pressure inside the reactor. The other method is to change the gas flow rate (GFR) used to produce the plasma jets. This leads to a T_vib reduction when the GFR is increased in the case of using helium or nitrogen as the working gas, but the opposite happens (an increase in the T_vib values) when argon is used, with different phenomena causing the variation of T_vib in each situation.     

纳秒脉冲表面介质阻挡放电特性实验研究

在常规大气环境条件下,基于单极性纳秒脉冲电源对表面介质阻挡放电特性进行了实验研究。结果表明:纳秒脉冲表面介质阻挡放电的本质是丝状放电,放电集中在电压脉冲的上升沿;激励电压和脉冲重复频率越大,放电越强烈,越接近均匀放电,但电压的作用更侧重于均匀性,而频率的作用则侧重于放电的强度;电极间隙的优化可以使表面介质阻挡放电特性最好;玻璃作为阻挡介质时容易发生沿面闪络。