Three-dimensional modeling of energy transport in a gliding arc discharge in argon

Abstract

In this work we study the energy transport in a gliding arc discharge with two diverging flat electrodes in argon gas at atmospheric pressure. The discharge is ignited at the shortest electrode gap and it is pushed downstream by a forced gas flow. The considered current values are relatively low and therefore a non-equilibrium plasma is produced. We consider two cases, i.e., with high and low discharge current-28 mA and 2.8 mA, and a constant gas flow of 10 L/min which has a significant turbulent component of the velocity. The study presents an analysis of the various energy transport mechanisms responsible for the redistribution of the Joule heating to the plasma species and the moving background gas. The objective of this work is to provide a general understanding of the role of the different energy transport mechanisms on the arc formation and sustainment, which can be used for the improvement of existing or new discharge designs. The work is based on a 3D numerical model, combining a fluid plasma model, the Shear Stress Transport Reynolds Averaged Navier-Stokes (SST RANS) turbulent gas flow model and a model for gas thermal balance. The obtained results show that at higher current, the discharge is constricted within a thin plasma column with several hundred of Kelvins above room temperature, while in the low current discharge, the combination of intense convective cooling and low Joule heating prevents discharge contraction and the plasma column evolves to a static non-moving diffusive plasma, continuously cooled by the flowing gas. As a result, the energy transport in the two cases is determined by different mechanisms. At higher current and constricted plasma column, the plasma column is cooled mainly by turbulent transport, while at low current and unconstricted plasma, the major cooling mechanism is energy transport due to non-turbulent gas convection. In general, the study also demonstrates the importance of turbulent energy transport in redistributing the Joule heating in the arc and its significant role for the arc cooling and the formation of the gas temperature profile. In general, the turbulent energy transport lowers the average gas temperature in the arc and thus it allows additional control of thermal non-equilibrium in the discharge.

Gliding Arc Reactor under AC Pulsed Mode Operation: Spatial Performance Profile for NOx Synthesis

“…The gas velocity decreased at a higher position where the gap between electrodes is larger, leading to less force to drag the arc toward the top of the reactor. This is in line with several studies in which the highest gas velocity was reported at the narrowest gap. , Besides the gas velocity, the influence of a thermal buoyant force could also play a role. Very often, the dominant role of a gas drag has been assumed in many reported studies due to the high flow rate used (several L/min to 10 L/min). , In our case, a low flow rate was applied (0.5 L/min), but the discharge gap is also narrow (in the mm range).…”

Advances in non-equilibrium $$\hbox {CO}_2$$ plasma kinetics: a theoretical and experimental review

“…Therefore, a compromise must be made, by reducing the kinetic scheme, to keep the calculation time feasible. Several 2D or 3D models for plasma reactors typically used for CO 2 conversion, such as (packed bed) DBDs, MW and GA plasmas, are therefore in first instance developed in simple gases (e.g., helium or argon, or sometimes air), with limited chemistry (e.g., [424][425][426][441][442][443][444][445][446][447][448][449][450][451][452][453][454][455][456][457][458][459]). This gives useful information, e.g., on electric field enhancement near the contact points of packing beads in a packed bed DBD [424,441,442], on streamer propagation in a packed bed DBD [425,426,[443][444][445][446], on plasma confinement in a MW plasma [447][448][449][450][451], or on arc behavior and gas flow patterns in a GA plasma [452][453][454][455][456][457][458]…”

Multi-dimensional modelling of a magnetically stabilized gliding arc plasma in argon and CO2

“…The cross section of the plasma without magnetic field and gas flow is simply a circle [36]. To illustrate the latter, we plot in Figure 7 the typical temperature distribution in a GDGA, calculated for a classical GA in Ar at 28 mA [49].…”