Distribution and evolution of surface charge in surface dielectric barrier discharge driven by AC and pulse dual power supply

The evolution of surface charge in surface dielectric barrier discharge (SDBD) is observed by using Pockels effect. SDBD is driven by sine AC and pulse dual-power supply voltage. The filamentary discharge and glow-like discharge are enhanced by superimposing positive pulse on sine trough and negative pulse on sine crest, respectively. The interval of enhanced discharge is adjusted by pulse repetition rate (PRF). The formation and decay of surface charges are analyzed at low PRF, and the accumulation effect is analyzed at high PRF. The results showed that the decay rates of charges decrease with increasing distance from the exposed electrode. When a positive pulse is superimposed on sine trough, the traces of positive charges are filaments with long extending lengths, which are the footprints of discharge channels. The lifetime of positive charges is hundreds of AC cycles (tens of milliseconds). Under certain conditions, subsequent glow-like discharge evolves as “flying” above the dielectric surface (3D propagation). Most of the negative charges are neutralized in subsequent filamentary discharge. Some negative charges accumulate downstream and exist longer than positive charges. In the case of negative pulses superimposed on sine crest, the enhanced glow-like discharge appears 3D propagation. The propagation distance is much smaller than that of positive pulse. Most of the negative charges are uniformly distributed near the exposed electrodes with a short lifetime (a few hundred microseconds) and are quickly neutralized in subsequent discharges. The occurrence of 3D propagation requires certain conditions and the mechanism needs further research.

Evaluation of Cylindrical Asymmetric Surface Dielectric Barrier Discharge Actuators for Surface Decontamination and Mixing

Surface dielectric barrier discharge (SDBD) was used to evaluate cylindrical plasma actuators for inactivation of Salmonella enterica. A cylindrical SDBD configuration was evaluated to determine if the inherent induced body force could be leveraged to impel plasma species, such as reactive oxygen and nitrogen species (RONS), as an apparatus to sterilize surfaces. The cylindrical structure is evaluated in this study to observe whether an increase in mixing is possible to efficiently distribute the plasma species, thereby improving bacterial inactivation efficiency. The increase in induced airflow of SDBD actuators with increased numbers of electrodes correlates with increased bacterial inactivation. These results suggest that improving the particle velocity, airflow mixing tendencies, and plasma volume for the same power inputs (same net power to the actuators) results in increased surface decontamination efficiency.