EXPERIMENTAL AND THEORETICAL RESULTS FOR LOW CURRENT D.C. ARC IN NOZZLE FLOWS AND CALCULATION OF COLD FLOW FIELD AND CORRELATION WITH EXPERIMENTAL DATA FOR ASYMMETRICAL FLOW CIRCUIT BREAKER NOZZLES (GAS DYNAMICS, NUMERICAL, FINITE ELEMENT METHOD)

To increase the basic knowledge concerning the interaction between the arc near current zero and the cold flow, investigations were conducted to determine the D.C. arc characteristics at a current of approximately 100 A in various nozzle geometries. 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.; A computer program based on the finite element method had been developed to calculate the subsonic flow field and the mass flux for the asymmetric dual-flow nozzle as well as the single-flow and symmetric dual-flow nozzles. The supersonic flow properties and the mass flux in the conical nozzle were also calculated by assuming the one-dimensional source flow. A characteristic method is used to design and calculate the supersonic nozzle contour which can generate smooth and axial flow at the nozzle exit. The flow field in this supersonic nozzle can also be calculated by the characteristic method and using a computer program.; The calculated results for the arc and the nozzle cold flow properties agreed well with the experimental measurements. It can be concluded that the convection cooling of the arc is the dominant arc cooling process for low currents. The computer program can provide a good tool in designing the arc interrupter nozzle.