Current zero behaviour of an SF₆gas-blast arc. I. laminar flow

Boundary layer type conservation equations have been used to investigate the zero current behaviour of an axisymmetric SF 6 arc burning in a supersonic nozzle. The theoretical model is based on local thermal equilibrium (LTE) and laminar flow. Arc conservation equations are solved for a current ramp before current zero and for a voltage ramp after current zero. Emphasis has been given to the relative importance of various energy transport processes during current zero period. Although there is a large discrepancy between theory and measurements, the results given in this paper are considered significant in that they demonstrate clearly the inadequacy of the conventional approach of supersonic arc modelling based on the aforesaid two assumptions.