DYNAMIC BEHAVIOR OF AN AC ARC COLUMN IN A STEADY LAMINAR ACCELERATING FLOW

The ac arc in a laminar flow subjected to a linearly increasing pressure gradient was studied by using simplified gas-property relations. The arc-conservation equations are solved numerically for sinusoidal current inputs by a full differential method, and, for comparison, by an approximate integral method. The dynamic behavior of the arc is found to be determined by two nondimensional parameters: the product of the frequency and the time scale of the flow OMEGA //F, and Z, which is proportional to the time scale of the flow divided by the square of the peak current. Of these, OMEGA //F is the more significant, and controls the relative importance of the energy transport by thermal conduction and that by convection in the electrically conducting core of the arc around current zero. Compared with the differential method, the integral method predicts all the qualitative features of the arc behavior, and good agreement is obtained for OMEGA //F greater than one. At low frequencies, however, the integral method tends to predict lower electric fields near the current zero, and the reignition peak occurs at a later instant.