Approved for public release; distribution unlimited. TECH OTHER it •#ew*ea>i Fluid Dynamics Facilities Rsch Lab aerospace Research Laboratories(AFSC »right-Patterson AFE, Ohio 45433 An experimental program has been conducted to investigate the physical processes occurring in vortex stabilized arcs, with and without an applied axial magnetic field. Arc temperature measurements indicate centerline temperature to be insensitive to arc current and chamber pressure. Centerline temperature was found to decrease when arc length was increased, when orifice area was decreased and when axial magnetic field strength was increased. Magnetic field strength could only be increased tu a "critical" value, at which point the discharge moved off the centerline line of the chamber and attached to its walls. A "stability criterion" has been derived to estimate the strength of the "critical" magnetic field. Experimental data agrees very well with the derived expression. Measurements have been made to determine arc "optical" diameter. There was an "apparent" increase in arc diameter when the magnetic field was applied which got larger as the field strength was increased. However, high speed resolution of light intensity from the arc indicated that arc diameter did, in fact, not increase but that the arc went into a helix. Helix diameter increased as magneti field strength increased. Heat flux measurements indicate that it is possible to reduce conduction and convection losses from the arc to zero except at the electrodes and in the nozzle. The radiation measurements indicate that it is possible to reduce radiation losses from an arc by increasing arc length, making the flow through the orifice a minimum and by using as strong an axial magnetic field as is possible.
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