【作者】 张禹涛；

【导师】 马腾才；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2007， 博士

【摘要】 非平衡等离子体中含有大量电子、亚稳态离子、自由基等活性粒子，具有极强的反应活性，电子能量很高，可达10 eV以上，但是气体温度低，一般约为几千K甚至接近室温，因此可以降低反应的门槛，在低温下引发很多化学反应。非平衡等离子体含有大量带电粒子，电子和离子质量差异很大，具有各向异性的能量分布，因此可以很灵活地通过外加电磁场控制其能流方向。由于具有上述特点，非平衡等离子体己经获得了广泛的应用。常压空气放电非平衡等离子体，例如电晕放电、介质阻挡放电和辉光放电等离子体不需要真空系统，不需要惰性气体，大大降低了运行费用，呈现出良好的发展势头。由于等离子体放电发展过程的正反馈特性，常压空气粒子密度高，放电容易过渡到火花甚至弧光状态，因此等离子体的均匀性和稳定性对其应用具有重要意义，这一课题始终是非平衡等离子体研究领域的热点之一。为改善常压空气非平衡放电等离子体的均匀性和稳定性，本文以电容耦合放电和介质阻挡放电为基础，开展了以下工作：1．提出阻容耦合空气中大气压辉光放电产生方法，利用阻容耦合负反馈原理，通过耦合电容建立反向电场，逐渐熄灭放电；引入耦合电阻增加放电回路的时间常数，和阻尼放电引起的高频振荡，成功抑制了等离子体放电发展正反馈机制引起的辉光放电向火花放电的过渡，分别在针-针、针-板和针-水电极发生器中产生了稳定的静态空气中大气压辉光放电。耦合电容变大会降低维持辉光放电的最高电压。耦合电阻对放电稳定性的影响存在一个最佳范围。二者对放电的影响是由放电回路时间常数决定的。适于产生辉光放电的范围由大到小依次是：针-针、针-水和针-板电极，即针-针电极稳定性最好，针-板电极最差。实验中发现采用电容耦合针-水电极，一定条件下会发生从火花放电向扩散电晕放电的过渡。考察了电极间距、电源频率和耦合电容等实验条件对过渡现象的影响，探讨了这种过渡发生的原因。2．研究了通过磁压缩线圈提供的动态阻抗提高介质阻挡放电电流脉冲的均匀性，当电压较低时动态阻抗可以有效降低电流脉冲幅值，并伴随着光辐射强度的降低和气体振动温度的升高。在此基础上引入阻尼电阻，产生了无丝介质阻挡放电，电流波形是光滑连续的正弦波。本质上它仍然是丝状流光放电，但是强度很弱。引入动态阻抗和耦合电阻的方法并不仅是改变了电流波形，而且是对等离子体的性质产生了深刻的影响。可以通过该方法调节DBD放电强度，从而拓宽了介质阻挡放电的应用范围。3．考察了纵向介质对常压下纳秒脉冲气体放电的影响。引入适当的纵向介质管明显增强了放电均匀性，增加了等离子体的空间范围，最大时可以增加到原体积的2倍，同时光向发展，同时介质表面的反向电场对放电起到负反馈作用，增强其均匀性。引入耦合电容有利于增强放电的均匀性和稳定性，但是对等离子体的规模没有影响。采用交流电源供电，对放电体积没有明显影响。产生差异的原因应该是两种供电方式产生的等离子体温度的不同，交流电源供电时因为气体温度高导致通道收缩。更多还原

【Abstract】 Non-equilibrium plasma has a lot of active particles, such as electrons, metastable ions, andradicals. It has strong reactive activity. In non-equilibrium plasma the electrons energy is veryhigh that may be beyond 10 eV, but the ions energy is very low that may be several thousands ofK, even room temperature, so the reactive threshold may be reduced, many reactions can occurin low temperature. Non-equilibrium plasma has a lot of charged particles, in which the mass ofelectrons and ions is very different, the energy distribution is anisotropy, so the energy flowdirection can be controlled by external electric and magnetic fields flexibly. Due to the meritsmentioned above non-equilibrium plasma has been applicated widely. Atmospheric pressure airnon-equilibrium plasma, such as corona discharge, dielectric barrier discharge and glowdischarge plasma does not need vaccum systym and noble gas, so the operating cost is reducedobviously, its prospect is very good. Because of the positive feedback characteristic of plasmadischarge development process and the particles density of atmospheric pressure gas is high,discharge is easy to transit to spark even arc, so the homogeneity and stability of plasma is veryimportant for its application, which has been a hot topic in plasma field. To improve thehomogeneity and stability of non-equilibrium plasma in atmospheric pressure air, the followingwork is done in this paper:1. Resisrance and Capacity-Coupled Glow Discharge for plasma generation method isproposed. According to the principle of Resisrance and Capacity-Coupled negative feedbackprinciple an anti-electric field is formed by the coupled capacitors, which can extinct thedischarge gradually; The coupled resistance can increase the time constant of the circuit andresist the high frequency oscillation caused by discharge, so the transition from glow to sparkcaused by the positive feedback mechanism of plasma development is prevented successfully, astable atmospheric glow discharge in static air is produced by using pin-to-pin, pin-to-plate, andpin-to-water generators, respectively. The increase of coupled capacity reduces the maximumvoltage for sustaining glow discharge. It exsists an optimal range with respect to the influence ofcoupled resistance on discharge stability. The influence of coupled resistance and capacity ondischarge is determined by the time constant of the circuit. According to the range for optimalgeneration of glow discharge the sequence is pin-to-pin, pin-to-water, and pin-to-plate generator,respectively. The transformation from spark discharge to diffuse corona discharge inatmospheric air is found in some conditions with a capacity coupled pin-to-water plasma reactor. The influences of power source frequency, inter-electrode gap, and coupled capacitance on thetransition are investigated. The reason for this transition is discussed.2. A study on improving the homogeneity of current pulse in DBD using active impedancegenerated by a magnetic compression coil is done. The peak current of DBD is reducedeffectively when the voltage is low. The intensity of optical emission spectra (OES) droped, andthe vibrational temperature of gas increased. On this basis DBD without filamentary pulse isproduced when a coupled resistance is introduced to the circuit. It is a weak DBD in the nature.The active impedance and the coupled resistance can change not only the current waveform butalso the nature of plasma. It has a profoundly effect on plasma. The intensity of DBD plasmamay be modulated by this method, so the application range of DBD plasma may be enlarged.3. The influence of a longitudinal dielectric on nanosecond pulse gas discharge is examined.An appropriate longitudinal dielectric tube can enhance the homogeneity, enlarge the scale ofplasma, the maximum ratio 2 is reached, the intensity of OES reduces to 29% of the original one(no dielectric is used). The homogeneity of discharge was enhanced further when a coupledcapacity is used. The longitudinal dielectric has no obvious effect on discharge using analtenative current power source. The reason should be ascribed to the difference of plasmatemperature caused by the two power sources, the constriction of discharge channel is found andthe scale of plasma is not enlarged when an altenative current power source is used.更多还原