Discharge dynamics in a cylindrical SDBD prototype reactor under ns-pulsed and sinusoidal AC operation

Abstract

We developed a prototype reactor generating surface dielectric barrier discharges (SDBDs) in ambient air, designed for consistent operation while preventing constructive material degradation. It features detachable stainless steel electrodes and quartz dielectric to ensure precise fabrication. The grounded electrode is fully immersed into transformer oil drastically suppressing undesired parasitic discharges. The device efficiently sustains ns-pulsed and AC discharges at 10 kHz, enabling fundamental studies of their electrical characteristics (applied voltage, induced current, electric power) and spatiotemporal dynamics (morphology, propagation length and velocity). The electric power (P) consumed exhibits a dissimilar non-linear increase with the rising peak voltage (Vp) in each case: P$\approx$0.8-2.5 W for ns-pulsed (Vp=7-9 kV) and P$\approx$0.9-5.3 W (Vp=7-10 kV) for AC operation. Using ICCD imaging, distinct ionization channels are recorded in the rising part of the pulsed voltage being detached from the driven electrode; during the voltage decrease, a glow-like discharge is formed remaining anchored on the driven electrode. The rising part of the AC voltage is characterized by erratic, elongated ionization channels in a filamentary form, the voltage drop featuring a glow-like behavior. During the rising and falling parts of the AC voltage, the discharge reaches maximum propagation lengths (Lmax) of $\approx$12 mm and $\approx$7 mm, respectively, while remaining attached to the driven electrode. The corresponding maximum discharge velocities (vmax) are about 5x10 2 m/s and 3x10 2 m/s. For the ns-pulsed operation, Lmax$\approx$5 mm (vmax$\approx$5x10 5 m/s) and Lmax$\approx$3.5 mm (vmax$\approx$1.5x10 5 m/s) during the rising and falling parts of the voltage pulse, respectively. The SDBD dynamics generated with a ns-pulsed voltage is more reproducible than for the AC case allowing for the use of a 500 times smaller ICCD gate width (2 ns) and a more accurate description of the discharge's spatiotemporal development. This reactor is suitable for performing fundamental studies and understanding key SDBD features for various applications such as flow control, biomedicine and agriculture.