A computational study on the energy efficiency of species production by single-pulse streamers in air

Abstract

We study the energy efficiency of species production by streamer discharges with a single voltage pulse in atmospheric dry air, using a 2D axisymmetric fluid model. Sixty different positive streamers are simulated by varying the electrode geometry, the pulse duration and the applied voltage. Between these cases, the streamer radius and velocity vary by about an order of magnitude, but the variation in the maximal electric field is significantly smaller, about 30%. We find that G-values for the production of N(4S), O(3P), NO and N2O, which have relatively high activation energies, vary by about 30% to 60%. This variation is mainly caused by two factors: differences in the fraction of energy deposited in the streamer head region, and differences in the maximal electric field at the streamer head. When accounting for both factors, our computed G-values are in good agreement with an analytic estimate proposed by Naidis (2012 Plasma Sources Sci. Technol. 21 042001). We also simulate negative streamers and find that their production of N(4S), O(3P) and NO is less energy efficient. The results suggest that energy efficiency can be increased by reducing Joule heating in the streamer channel and by increasing the maximal electric field at the streamer head, for example by using short voltage pulses with a high applied voltage.

Quantitative modeling of streamer discharge branching in air

“…We therefore expect background ionization from previous pulses to not significantly affect the branching behavior observed here. For more recent results on the effect of ion conversion and of electron attachment and detachment processes on the electron density in repetitive discharges, we refer to [48][49][50]. 105 ns (at 15 kV), 119 ns (at 17 kV) and 133 ns (at 19 kV).…”

Temporal evolution and mechanism of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage

“…The reaction set used in this paper is from [27], containing 263 chemical reactions and 56 species. The electron swarm coefficients and the rate coefficients of electron impact reactions are functions of the reduced electric field E/N, where E is the electric field and N is the gas number density.…”

“…The temporal evolution of electron conduction current, I e , at the anode and cathode and the total discharge current is shown in figure 7. The I e is computed as [27]:…”

“…Moreover, the energy efficiency of active species production varied temporally with the temporal evolutions of the streamer characteristics such as the streamer length, the reduced electric field (E/N) and the electron density (n e ). While extensive studies have focused on the temporal evolution of primary streamers [25][26][27][28], research on secondary streamers remains limited. Therefore, a thorough investigation into the temporal evolution of secondary streamers will contribute significantly to our understanding of the temporal variation in energy efficiency for the production of active species.…”

Double-pulse streamer simulations for varying interpulse times in air

“…We use the reaction set given in [35], containing 263 reactions, which was primarily compiled from the reactions given in [36,37]. This set includes reactions between electrons, neutrals, ions, and excited species.…”