A microwave-augmented plasma torch module

Abstract

A new plasma torch device which combines arc and microwave discharges to enhance the size and enthalpy of the plasma torch is described. A cylindrical-shaped plasma torch module is integrated into a tapered rectangular cavity to form a microwave adaptor at one end, which couples the microwave power injected into the cavity from the other end to the arc plasma generated by the torch module. A theoretical study of the microwave coupling from the cavity to the plasma torch, as the load, is presented. The numerical results indicate that the microwave power coupling efficiency exceeds 80%. Operational tests of the device indicate that the microwave power is coupled to the plasma torch and that the arc discharge power is increased. The addition of microwave energy enhances the height, volume and enthalpy of the plasma torch when the torch operates at a low airflow rate, and even when the flow speed is supersonic, a noticeable microwave effect on the plasma torch is observed. In addition, the present design allows the torch to be operated as both a fuel injector and igniter. Ignition of ethylene fuel injected through the centre of a tungsten carbide tube acting as the central electrode is demonstrated.