The Dependence of the Air Blast Arc Characteristics on Electrode Position

The effect of the position of the upstream electrode on the characteristics of the air blast arc in a converging-diverging nozzle is investigated using a simple one-dimensional model. It is found that altering the upstream electrode position affects the pressure gradient between the electrode and the nozzle throat. The pressure gradient in this region determines to a large extent the arc area contraction rate as the arc current decreases to zero and, therefore, the interruption capability of the arc after current zero. Moreover, the upstream electrode position affects the arc diameter in the steady and transient states throughout the whole arc length. It is found that radial turbulent cooling need not be incorporated into the model to explain the experimental results. However, turbulent radial cooling, if present, is found to enhance the interruption capability of the arc by a large factor.