Experimental characterization of plasma synthetic jet actuators

Among the various active flow control techniques, Plasma Synthetic Jet (PSJ) actuators, or Sparkjets, represent a very promising technology, especially for their high velocities and short response times. A practical tool, employed for design and manufacturing purposes, consists in the definition of a low-order model, lumped element model (LEM), which is able to predict the dynamic response of the actuator in a relatively quick way and with reasonable fidelity and accuracy After a brief description of an innovative lumped model, this work faces the experimental investigation of a home-designed and manufactured PSJ actuator, composed of two parts in Macor and two tungsten electrodes, working at different frequencies and energy discharges. Particular attention has been taken in the power supply system design. It is mainly composed of a high-voltage trigger device and an external supply system (sustain device), which provides electrical power to the first one. The purpose of the former circuit is to momentarily reduce the local breakdown voltage between the electrodes and to define the actuation frequency; the amount of energy provided to the fluid in each cycle can be controlled with the external power supply, by varying the sustain circuit voltage, or through a Mosfet transistor, by changing the discharge duration. A specific house-made Pitot tube has allowed the detection of velocity profiles along the jet radial direction, for various axial locations, as well as the tuning of the lumped model with experimental data, where the total device efficiency has been assumed as a fitting parameter. The best fitting value is tot = 0:45, which closely agrees with classical literature values.