Simulation of transient and zero current behavior of arcs stabilized by forced convection

A one dimensional arc model has been used to calculate the transient characteristics of an arc stabilzed by forced convection in a supersonic nozzle. The axial profile of the central temperature arc radius and the electric field in the arc are determined as the current is decreased from 2000 A at the rates of 24 A/µs and 48 A/µs to zero current, after which calculations are carried out for about 10 µs in the absence of current. The interruption capability of the arc in the two cases is tested in the presence of a recovery voltage applied across the arc starting at zero current for various values of rate of rise of recovery voltage (R.R.R.V.). Very good agreement with experiment is obtained. The calculations indicate that turbulence is a very important energy loss mechanism at small currents; and particularly at zero current, radial turbulent conduction is the dominant energy loss mechanism. However, at large currents (greater than 500 A), turbulence is shown to contribute very little towards determining the arc characteristics. In the high current regime, radiation and axial convection are the dominant energy loss mechanisms.