Electric arc stabilization in crossed convective and magnetic fields.
An experimental study of the behavior of an electric arc in crossed convective and magnetic fields has been made and the results compared with a theory developed by Cowley for such arcs. The arc, of 7 to 70 amp, was held stationary between two parallel rail electrodes, mounted in a small wind tunnel, with nitrogen as the working gas. The velocity in the test section ranged between 0 and 40 m/sec, and the corresponding magnetic field between 0 and 500 gauss. A drag coefficient, based on the measured dimension of the arc transverse to the flow, was found to depend, in this range of parameters, on the freestream Reynolds number based on the same dimension and to have values between 0.82 and 1.8. The stable configuration for the arc was with the column slanted across the electric-field lines, the cathode spot downstream of the anode spot. The slant of the arc has been related to the widening of the column near the downstream electrode. Nomenclature B = magnetic field strength, gauss CD = drag coefficient of arc column D = measured arc dimension transverse to gas flow, mm E = electric field, v/m h = enthalpy, nm / = arc current, amp j = current density, amp/m2 M = Mach number •P = pressure, n/m2 R = characteristic dimension of column, m Re = freestream Reynolds number AS = area between adjacent field lines, m2 T = temperature, °K Um = freestream velocity, m/sec UQ = characteristic velocity in shear layer, m/sec VQ = characteristic velocity in core, m/sec 5 = boundary-layer thickness, m po = characteristic density for gas in column, kg/m3 PCO = freestream density, kg/m3 a = conductivity, mho/m /z = viscosity, kg/m X sec no = characteristic viscosity in core, kg/m X sec