Scaling Laws for Electric Arcs Subject to Forced Convection

The positive cloumn voltage (phi) of an arc is investigated under conditions of cylindrical geometry and forced convection of Ar or N gas. An expression for phi is found as a function of properties of the gas and the geometry. It is shown that if the electrode length and the total arc current are multiplied by an arbitrary factor alpha, and the mass flow/unit area and the pressure are multiplied by 1/alpha, phi is invariant. This phi invariance scaling law is studied experimentally. (T.F.H.)