Operational characteristics of a periodic plasma torch

Development of a plasma torch, which is intended as an ignition aide within a supersonic combustor, is studied. The high-voltage discharge and plasma plume generated by the torch module are described in a quiescent environment and in a supersonic crossflow. Voltage-current characteristics of the discharge and optical images of the plasma plume are used to characterize the operation of the torch module. The principal advantages of this torch module are its compact design, durability, and operational flexibility. The torch module can be operated in periodic or pulsed modes, depending on the power supply used. In the periodic mode presented in this paper, the capacitors are charged at the line frequency of 60 Hz resulting in a cyclical discharge at a frequency of 120 Hz. In this mode, peak and average powers reaching 8 and 2.8 kW, respectively, are demonstrated. The energy can be as high as 46 J per cycle, which is mainly limited by the power handling capability of the power supply. The penetration height and the volume of torch plume into a Mach 2.5 supersonic flow, typical for a supersonic combustor startup condition (vis-à-vis the cross-flow velocity), are investigated. In addition, ignition of ethylene fuel in a Mach 2 supersonic flow with a total temperature of 590 K and pressure of 5.4 atm is demonstrated.