Ben Li

Periodic-driven vibration of discharge filaments induced by surface charges in a dielectric-barrier discharge

The periodic-driven vibration of filament pairs in a dielectric-barrier discharge (DBD) pattern is investigated with successive discharges by a high-speed camera. Images correlated with successive half-driven cycles present three representative types of vibrations of the filament pairs, i.e. vibration along a line, vibration with orientational changes and vibration with a ‘stop’. Based on the time-reversal discharge order of the paired filaments, which is demonstrated by images correlated with successive discharge current pulse phases, the involved physics of the vibration is explained by analysis and simulation of the electric field influence induced by surface charges of the filament pairs. Finally, this vibration is proved to be in good agreement with the phenomenon observed from time-integrated images. Moreover, from these results, three general conclusions for filamentary structures in streamer DBDs are obtained and a ‘preferential discharge’ mechanism is proposed, which is further development of the ‘memory effect’ of surface charges.

Hexagonal superlattice pattern consisting of colliding filament pairs in a dielectric barrier discharge

Colliding-pairs hexagonal superlattice pattern (CPHSP) is studied in a dielectric barrier discharge system. The evolution of CPHSP bifurcating from a hexagonal pattern to chaos is shown. The phase diagrams of CPHSP as a function of discharge parameters are given. From a series of pictures taken by a high speed video camera, collisions between two spots are observed and the superposition of many collisions results in each big spot presenting four small spots on long time scales. Measurements of the correlation between filaments indicate that the pattern is an interleaving of four different transient hexagonal sublattices. Depending on the discharging sequence, the forces exerted on one colliding spot are discussed briefly.

Honeycomb superlattice pattern in a dielectric barrier discharge in argon/air

We report on a honeycomb superlattice pattern in a dielectric barrier discharge in argon/air for the first time. It consists of hexagon lattice and honeycomb framework and bifurcates from a hexagon pattern as the applied voltage increases. A phase diagram of the pattern as a function of the gas component and gas pressure is presented. The instantaneous images show that the hexagon lattice and honeycomb framework are ignited in turn in each half voltage cycle. The honeycomb framework is composed of filaments ignited randomly. The spatiotemporal dynamics of honeycomb superlattice pattern is discussed by wall charges.

On the mechanism of pattern formation in glow dielectric barrier discharge

The formation mechanism of pattern in glow dielectric barrier discharge is investigated by two-dimensional fluid modeling. Experimental results are shown for comparison. The simulation results show that the non-uniform distribution of space charges makes the discharge be enhanced in the high-density region but weakened in its neighborhood, which is considered as an activation-inhibition effect. This effect shows through during a current pulse (one discharge event) but also in a certain period of time after discharge that determines a driving frequency range for the non-uniformity of space charges to be enhanced. The effects of applied voltage, surface charge, electrode boundary, and external field are also discussed. All these factors affect the formation of dielectric-barrier-discharge pattern by changing the distribution or the dynamics of space charges and hence the activation-inhibition effect of non-uniform space charges.

Investigation on motional characteristics of paired filaments in a dielectric barrier discharge by a high-speed framing camera

Motional characteristics of paired filaments in a hexagonal superlattice pattern in a dielectric barrier discharge are investigated by a high-speed framing camera. Through images correlated with successive current pulse phases, the change in position of the paired filaments is observed, and the time-reversed sequence of the appearance of the paired filaments is determined. Generally, the first ignited spot moves closer to their centre, while the second ignited spot moves further from it, and the distance between the two spots does not change significantly. Sometimes only one filament has obvious changes in position, leading to the variation of distance and orientation of the pair. Based on the appearance sequence, the change in position of the paired filaments is explained by the interaction of internal fields induced by surface charges. The statistics of the variations of the distance D between the paired filaments are investigated within successive discharges.

Investigation on collisions of filament pairs in dielectric barrier discharge

Collisions of filament pairs in a hexagonal superlattice pattern in dielectric barrier discharge are investigated on different timescales. In the evolution of the pattern, the space scale of each hexagon cell decreases with the increasing voltage. The duration of one collision is seven half voltage cycles at least. Two stable orientations of a pair are approximately perpendicular to each other and the orientational changes occurring during the entire colliding process should be a multiple of 30°. The time interval between two consecutive collisions decreases with the increasing voltage. The distance between the paired spots decreases nonmonotonically. Based on the discharge order of the pattern, it is inferred that the collision should be the interaction between a discharging filament and the surface charges deposited by another discharged filament, and the nonmonotonic decrease of distance D is explained.

Interactions between surface discharges induced by volume discharges in a dielectric barrier discharge system

The interaction between micro-discharges involved in surface discharges (SDs) is studied in dielectric barrier discharge system. Instantaneous images taken by high speed cameras show that the SDs are induced by volume discharges (VDs). They cannot cross the midperpendicular of two neighbouring volume charges at low voltage while they stretch along it at high voltage, indicating that there is interaction between SDs. The differences of plasma parameters between SD and VD are studied by optical emission spectroscopy. The simulation of the electric fields of the wall charges accumulated by VD further confirms the existence of the interaction.

Spatiotemporal characteristics of a patterned dielectric barrier discharge controlled by various mechanisms

In this paper, we present a comprehensive discussion on various mechanisms collectively controlling the spatiotemporal characteristics of a patterned dielectric barrier discharge. High-speed images correlated with current pulse phases show that the square pattern is composed of two interleaving square sublattices with a time-reversal symmetric discharge order, whose spatial and temporal stabilities are explained by surface-charge–induced activation-inhibition mechanism. Images of 100 ns order demonstrate the localized synchronicity of the development of one single sublattice, which may be attributed to photo-ionization. Through the investigation of light emissions of the two sublattices, a surface-charge sharing mechanism is proposed, which is also responsible for the stability of the patterned discharge.

Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.