Diagnostics on Steady-State Cross-Flow Arcs

A novel cross-flow arc system has been developed which permits the attainment of repeatable arc configurations, oriented in the vertical plane containing the horizontal upstream flow vector, symmetrical in cross section, and symmetrical with respect to the midlocation between the electrodes. A bow-shaped arc is found at lower currents (less than about 20 amperes); a cusp-shaped arc is obtained at higher currents (greater than about 40 amperes). A transition regime is observed at intermediate levels. A unique optical system has been developed in order to observe the arc simultaneously at many different azimuthal locations. With this system, and with the aid of an inversion method developed in [8], isotherm distributions within the arc have now been obtained for the first time. These isotherms, obtained in a horizontal plane near midlocation between the electrodes, indicate that the arc may be divided into a central core region, nearly circular in cross section, and an outer region wherein convective exchange probably predominates. For a given average through-flow velocity, the extent of the central core becomes greater as the current is increased. The cross-flow arc appears noncircular in cross section, with the major axis oriented in the direction of flow. The experiments were conducted in argon (at atmospheric pressure), at constant speed (43.8 cm/s), and constant electrode spacing (6.64 mm); arc current was varied in the range between 17.2 and 34.1 amperes.