Analysis of Thermal Recovery for SF6 Gas-Blast Arc within Laval Nozzle

Abstract

In this paper we describe a method of estimating the thermal recovery characteristics in a Laval nozzle. The post arc current was calculated according to the decreasing rates of current and the upstream pressures. A two-dimensional differential arc model was used to analyze the arcing phenomena. The radiation energy transport and the turbulence effects were calculated using the semi-experimental arc radiation model and the Prandtl mixing length model, respectively. The electric field and the magnetic field were calculated with the same grid structure used for the simulation of the flow field. The arc model has been coded into “PHOENICS” which is a commercial computational fluid dynamics (CFD) program. In order to investigate the thermal recovery characteristics after current zero, the simulation of steady-state arc of 1000 A DC, the simulation of transient arc generated by the current which decreases with the rate of di/dt=27.0 and 13.5 A/µs before current zero, and the simulation of hot-gas flow were carried out in an upstream pressure range of 0.68–6.82 MPa. The obtained results were verified by comparison with the test results presented by the research group of GE Co. (General Electric Company).