Magnetic field stabilization of low current DC arc discharge in cross flow in argon gas at atmospheric pressure—a numerical modelling study

Abstract

In this work we study the effect of an external magnetic field and gas flow on the properties of a low current DC (gliding) arc discharge in argon at atmospheric pressure. We consider a cross flow configuration, in which argon gas flows perpendicularly to the arc current, while the external magnetic field is perpendicular to both the arc current and the gas flow. The study is based on a 2D numerical fluid plasma model of the discharge, coupled with a gas flow model based on the Navier-Stokes equations and a gas thermal balance equation. In the examined configuration, a stabilized arc is achieved by having the E × B drift acting in opposite direction to the gas flow, i.e. the Lorentz force pushing the arc against the gas flow. The numerical model was implemented into a finite element simulation, using the Comsol Multiphysics R (version 5.3) package. The results proved that a magnetically stabilized arc can be sustained and that the examined configuration can be used for effective gas treatment. The analysis of the simulation data helped to answer multiple questions, related to arc stability, the energy density distribution in the arc, and the macroscopic properties of the system as a whole. The results show a significant influence of the walls on the arc stabilization, while in the case of walls positioned very far from the arc, i.e. unbounded channel, the arc becomes a source of a fluid instability, causing vortex shedding. In general, this study provides insight on the interaction between the gas flow and the arc in a strong magnetic field. The model presented here has the potential to further the understanding of magnetically stabilized discharges and to become a basis for developing similar studies of more complex gases.

Conversion of CO2 in stabilized low-current arc discharge at atmospheric pressure

“…We were also able to show that the results from this study match the predictions in [5]. The simulation results from [5] give us an estimate for the arc parameters in the case of a laminar flow under similar conditions. The predicted behavior of the arc-to-wall attachment matches our experimental observations.…”

“…The conditions here correspond to the case of a 4-mm distance between the dielectric glasses in [5]; qualitatively, the discharge in the experiments shows the same behavior -the arc is stabilized near one of the dielectric walls and not in the middle. In [5], it is shown that the increase in the gas velocity, i.e., the gas flow, leads to a decrease in the gas temperature, a thinner arc column (reduced radius) and to the effect mentioned whereby the arc gets pushed to one of the side walls. These effects can lead to the conversion reduction seen in figure 3 (a) in several ways: i) the arc column has a smaller crosssection in the flow direction, so that a lesser amount of gas passes through it and therefore less of the gas is treated, ii) the gas that enters the arc column remains in the arc region for a shorter time, iii) the near arc region has a lower average temperature.…”

“…The decrease in the conversion rate in figure 3 (a) can be explained if we refer to the results in [5]. The conditions here correspond to the case of a 4-mm distance between the dielectric glasses in [5]; qualitatively, the discharge in the experiments shows the same behavior -the arc is stabilized near one of the dielectric walls and not in the middle.…”

“…The decrease in the conversion rate in figure 3 (a) can be explained if we refer to the results in [5]. The conditions here correspond to the case of a 4-mm distance between the dielectric glasses in [5]; qualitatively, the discharge in the experiments shows the same behavior -the arc is stabilized near one of the dielectric walls and not in the middle. In [5], it is shown that the increase in the gas velocity, i.e., the gas flow, leads to a decrease in the gas temperature, a thinner arc column (reduced radius) and to the effect mentioned whereby the arc gets pushed to one of the side walls.…”

“…The configuration of a magnetically-stabilized arc was studied theoretically in [5] as a means of revealing the general trends in the arc behavior and the conditions for arc stabilization. These results were obtained in argon, but it is expected that the gas flow-arc interaction should remain qualitatively similar so that the results in [5] can be used to provide a general understanding of the experimental results obtained here.…”