Circuit studies for cyclotronic plasma actuators

Recent experimental research has been aimed at flow control using plasma arc breakdown in a magnetic field. An innovative new actuator technique produces a high-voltage plasma arc across a coaxial pair of electrodes positioned within the field of a strong rare-earth ring magnet. Plasma arc generation within a magnetic field perpendicular to the current path causes Lorentz forcing on the charged particles, such that the arc sweeps about the center of the coax. Thus, the rotating plasma arc interacts with the surrounding flow, creating vortices. Being similar in concept to microwave-generating cyclotron elements, the resulting actuator concept has been designated as a “Cyclotronic Arc-Plasma Actuator”. This innovative concept couples the thermal actuation of the plasma arc filament along with the swirl component produced by the angular velocity of the Lorentz forcing. Arrays of this actuator configuration can be applied in boundary layer flow control to alleviate turbulent flow separation, serving as a controllable vortex generator that can be enabled or disabled on-demand. Parasitic drag penalty during high speed cruise can be eliminated by embedding the devices spanwise in an aerodynamic surface, and activating the actuator arrays only during critical takeoff and landing phases. A current objective is to develop practical circuits which can be used to power the actuator arrays, such that these can be demonstrated in realistic flows, applying the devices in wind tunnel models and on UAV platforms. The paper examines specifically the frequency tuning of zero-voltage switching networks to operate between 40 kHz and 100 kHz. For DC power input between 35 and 160 W, the rotation rates vary from 2000 to 5500 RPM, with a significant dependence on the operating frequency Operation of arrays of actuators from battery supplies, as well as integration efforts for an experimental UAV are also described.