The LTE Thermofluid Simulation of Ar/SF₆ Gas-Blast Arcs in a Nozzle Space in an Arc Device

Abstract

The present paper describes numerical thermofluid simulation results of SF 6 , Ar, and Ar/SF 6 arcs in a nozzle space at atmospheric pressure on the assumption of local thermodynamic equilibrium (LTE) condition. It is crucial to investigate fundamentals on arc extinction phenomena by numerical simulation approach as well as experimental approach. Two-dimensional temperature distributions in SF 6 , Ar, Ar/SF 6 gas-blast arcs were calculated in a steady state at a direct current of 50 A. Furthermore, transient temperature distributions in these arcs were computed under free recovery condition for a fundamental study. We investigated dependences of the gas mixture ratio of SF 6 to Ar and the gas flow velocity on the arc temperature and the arc voltage. The calculated arc voltage in the steady state and the transition of electron density under free recovery condition were compared with those obtained by laser Thomson scattering method in our experiments. As a result, the increasing admixture ratio of SF 6 to Ar and the increasing gas flow velocity shrinks the arc plasma around nozzle throat inlet, leading to the higher arc resistance. Under free recovery condition, the arc plasma decay more rapidly there. Comparison in electron density shows the similar dependence on SF 6 and Ar, while there is still some difference in the absolute value of electron density between the calculation results and experimental results.

Measuring Density Profiles of Electrons and Heavy Particles in a Stable Axially Blown Arc

“…The main factor, however, is probably the lower arc temperature of 13 000 K calculated in Ref. [38] for the experimental conditions in Ref. [20].…”

“…Our results can be compared with a previous measurement of the electron density in an axially blown arc [19,38]. In that work, measurements at several radial points were performed using Thomson scattering for an arc cooled by a constant volume flow of argon of 100 l=min at a pressure of approximately 1 bar.…”

Numerical thermofluid simulation of a decaying arc behavior in CO2/O2/C5F10O (C5‐PFK) considering more than nona‐atomic molecules

“…Figure shows the cross section of the nozzle space in our arc device, which we have been using for a fundamental study for arc discharges A half area of this cross section was treated as calculation domain, which is a cylindrical axisymmetric two‐dimensional area. The calculation domain size is 170 × 50 mm.…”

“…In addition, successful or failure interruption is determined in very short time of the order of µs. For this reason, it is important to study the arc extinction phenomena in detail with both experimental and numerical simulation approaches . In our previous experimental approach, we established a new system of decaying arc plasmas using a direct‐current power source and an insulated gate bipolar transistor .…”

“…On the other hand, numerical simulation has been widely adopted for arc simulation nowadays. In our numerical approach, we developed a numerical thermofluid local thermodynamic equilibrium (LTE) model . The LTE model is very useful to understand arc behavior roughly including mass and energy transport in the fluid.…”