【作者】 张定宗；

【导师】 王德真； 王艳辉；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2013， 博士

【摘要】 大气压介质阻挡放电中存在着非常复杂的时间非线性行为,如倍周期分岔与混沌。在这些行为中,放电电流每多个电压周期重复一次或者随外加电压随机振荡。它们对放电参数比较敏感,与放电的稳定性密切相关,直接影响到大气压介质阻挡放电的应用。研究这些行为对如何获得稳定的放电有着非常重要的指导意义,因而近些年来,受到了较为广泛的关注。在本论文中,先后采用一维和二维的流体力学模型,对大气压介质阻挡放电中的时间非线性行为与空间演化特性进行了研究。具体分为以下五个部分：(a)同轴电极介质阻挡放电的特性与时间非线性行为研究；(b)平行板电极介质阻挡多峰放电中的时间非线性行为研究；(c)对称的单周期放电转变到二倍周期放电的机理研究；(d)二倍周期放电的物理机制及其空间演化特性研究；(e)脉冲介质阻挡放电中两次放电的空间演化特性研究。第二章,采用一维流体模型模拟研究了同轴电极结构中介质阻挡放电的特性与时间非线性行为。研究发现：在通常的单周期放电内正负半周期的放电电流是不对称的,放电的不对称程度主要由两个电极的半径比决定。在一定的条件下,放电随着频率或气体间隙的变化会呈现出倍周期分岔、二次分岔、混沌等复杂的时间非线性行为。第三章,深入研究了大气压平板电极结构中介质阻挡放电的时间非线性行为。模拟发现：与单峰放电相似,多峰放电中也存在倍周期分岔以及混沌等时间非线性现象。然而在多峰倍周期分岔序列中,多峰只出现在半个电压周期内(或电压的正半周期或电压的负半周期)。当正负半周期的放电不对称时,放电对参数十分敏感,很容易过渡到其他放电状态。反之,放电相对稳定。对于稳定的倍周期状态,改变参数可使半个电压周期内的放电次数增加而不改变其周期态。第四章,模拟研究了单周期放电分岔进入倍周期放电的转换机制。结果显示：在一个对称的单周期放电进入倍周期放电前,它总是先偏离其正常的对称放电模式而进入一个正负半周放电不对称的单倍周期放电状态。然后,随着参数的变化,不对称放电中较弱的放电将逐渐变强,直到这个放电削弱下一次放电并导致放电发生分岔进入倍周期放电状态。在整个转换过程中,每次放电前电子密度、离子密度和电场强度的空间分布状态起到了决定性的作用。第五章,采用二维流体模型对二倍周期放电形成的物理机制及其空间演化特性进行了研究。结果表明,放电空间局部高的电子密度区域的产生是形成二倍周期放电的主要原因。当局部高电子密度区域出现在瞬时阳极附近时,它对接下来的放电影响很小。相反,当局部高电子密度区域出现在瞬时阴极附近时,它将限制放电空间场强的增长,从而导致接下来的放电变小。这种局部高电子密度区域每两个电压周期重一次,从而导致放电呈现出二倍周期放电。在二倍周期放电中,四次放电都有着各自不同的空间演化行为。由非均匀的介质表面电荷引起的径向非均匀场强是导致这些空间演化的主要原因。第六章,模拟研究了脉冲介质阻挡放电中两次放电的空间演化特性。结果发现：脉冲放电中的两次放电既能处于沿径向均匀的放电模式,又能处于沿径向不均匀的放电模式。放电的均匀性主要由前次放电的性质以及前次放电与本次放电之间的时间间隔决定。如果前一次放电结束时,电子密度沿径向是均匀分布的,两次放电之间的时间间隔越短,接下来的放电就越均匀。两次放电的时间间隔主要取决于电压脉冲频率和脉冲宽度,相对而言,脉冲频率越高,主放电越均匀；而脉冲宽度越小,次放电越均匀。更多还原

【Abstract】 Atmospheric-pressure dielectric-barrier discharges (DBDs) possesse complex temporal nonlinear behaviors, such as period-doubling bifurcation and chaos. In these nonlinear behaviors, the discharge current pulses repeat at multiple applied voltage cycles or fluctuate stochastically. These behaviors are sensitive to discharge parameters and closely related to the discharge stability, which affect directly the applications of the atmospheric-pressure DBDs. The studies of these nonlinear behaviors can provide important references for realizing stable discharge. Hence, in recent years the complex temporal nonlinear behaviors of atmospheric-pressure DBDs have received considerable attentions.In this paper, the temporal nonlinear behaviors and characteristics of spatial evolution in atmospheric-pressure DBDs are investigated using one-dimensional or two-dimensional fluid models. The finished studies include the following sections:(a) the characteristics and temporal nonlinear behaviors of DBD between two coaxial electrodes;(b) the temporal nonlinear behaviors of DBD with multiple current pulses per half voltage period between two parallel planar electrodes;(c) the transition mechanisms from a symmetric single period discharge to a period-doubling discharge;(d) the mechanisms and spatial evolutions of the period-two discharge;(e) the spatial evolutions of two discharges in pulsed DBD.In chapter2, based on a one-dimensional fluid model, the discharge behaviors and spatial evolutions of atmospheric-pressure DBD between two coaxial electrodes are studied. It is found that the discharge currents are always asymmetrical during the positive cycle and negative cycle of the applied voltage and this asymmetry is mainly decided by the ratio of two electrode radii. Under certain conditions, with the variation of the frequency or gas gap the discharges can assume complex nonlinear behaviors including period-doubling bifurcation, secondary bifurcation and chaos.In chapter3, the temporal nonlinear behaviors of the atmospheric-pressure DBD between two parallel planar electrodes are investigated. The results show that complex nonlinear behaviors such as period-doubling bifurcation and chaos can also be observed in the DBD with multiple current pulses per half voltage period. In the sequence of the multi-pulse period-doubling bifurcation, the multiple current pulses appear only in the half voltage cycle (in positive or negative half cycle). When the discharge becomes asymmetrical it is sensitive to the discharge parameters, and can be easily changed into other discharge states. Othervise, the discharge is relatively stable, and can sustain over a broad parameter range. In a certain range, changing parameters will result in the increase of the number of current pulses while not change its periodic state.In chapter4, the transition mechanism from a symmetric single period discharge to period-doubling discharge are studied. The simulation results show that before a discharge bifurcates into a period-doubling state, it first deviates from its normal operation and transforms into an asymmetric single period discharge mode. After that, the weaker discharge in the asymmetric discharge will be enhanced gradually with the changing of the parameters until it weakens the following discharge and results in the discharge entering a period-doubling discharge state. In the whole transition process, the distributions of the electron density, ion density and electric field before the discharge starts play a definitive role.In chapter5, the mechanisms of period-two discharge and its spatial evolutions are studied using a two-dimensional fluid model. The results suggest that the production of the local high electron density region in discharge space is the main reason for the formation of the period-two discharge. When the local high electron density region appears near the momentary anode, it barely affects the subsequent discharge. In contrast, when the high electron density region appears in the vicinity of the cathode, it reduces the subsequent discharge current greatly. If the local high electron density region repeats every two voltage cycles, the discharge will assume period-two state. The four discharges in a period-two discharge have different spatial behaviors. Non-uniform electric field along the radial direction induced by non-uniform surface charge densities are the main reason causing these spatial behaviors.In chapter6, a two-dimensional fluid model is developed to study the spatial evolutions of the two discharges in pulsed DBD. The results show that the two discharges ignited during one voltage pulse can operate in either radially uniform or radially nonuniform manner. This is mainly determined by the previous discharge characteristics and the time intervals between this discharge and its previous discharge. If the electron density distribution is radially uniform at the end of the previous discharge, the shorter the time interval between two discharges, the more homogenous the subsequent discharge. In pulsed discharge, the time intervals between two discharges are mainly determined by the duration and repetition frequency of applied voltage pulse. The higher the repetition frequency is, the more uniform the primary discharge is. The shorter the duration is, the more uniform the secondary discharge is.更多还原