Experimental and Theoretical Study of a D.C. Arc in a Constant Diameter Nozzle Flow

The cold air flow field for a 1.27 cm constant diameter nozzle was determined for subsonic and transonic flow velocities. In addition, d. c. arc voltage, current and diameter measurements were made for an arc gap of 5.52 cm and a current of approximately 100A. Arc voltage increased rapidly as the flow velocity increased from zero to sonic velocity. Using a channel flow model with constant arc temperature and the energy integral for the convective cooling, analytical expressions were derived for the arc radius, electric field strength, arc voltage, resistance, and power as functions of the cold flow properties, current, and axial distance. Calculated arc voltages, resistances, and powers compare favorably with measured values.