Prediction of properties of arcs stabilized by forced convection

Abstract

A one-dimensional arc model has been used to calculate the central temperature, arc radius, and electric field as a function of axial position for steady-state arcs in forced convection in nozzles. Calculations indicate that the axial distributions of pressure, plasma velocity, and gas velocity are sensitive to the degree of gas heating by the arc of the surrounding gas, significant differences being obtained between assumptions of the gas being isothermal or expanding adiabatically. Despite the fact that turbulence effects are omitted in the model, good agreement is obtained with experimental results of arc temperature, radius, and electric field for a 2000-A arc in nitrogen. Calculations as a function of current indicate regimes of low, intermediate, and high current where arc voltage respectively decreases, is constant, and increases with increase of current. In the latter regime, the increase in voltage is caused by the arc ’’clogging’’ or restricting the gas flow in the nozzle.