Sammendrag
This paper reports on experiments with ultra-high pressure nitrogen arcs in a self-blast type switch design. The effect of filling pressure on nozzle mass loss and pressure-rise in the heating volume is investigated. An arc current peak of 130 A at 190 Hz, and a fixed inter-electrode gap of 50 mm are used. The arc burns inside a polytetrafluoroethylene nozzle with a gas outflow vent in the middle. Three different nitrogen filling pressures were tested: 1, 20 and 40 bar, which also covers the supercritical region. To study the effect of vent size on blow pressure near current zero, three different vent dimensions were investigated. The energy deposited in the arc increases with the filling pressure. It is observed that the pressure-rise in the heating volume is linked to the filling pressure, while the vent size plays a crucial role in the blow pressure near current zero. The nozzle mass loss per unit energy deposited in the arc is found to be independent of the filling pressure.