Recent Performance-Based Advances in SparkJet Actuator Design for Supersonic Flow Applications

Effect of slotted exit orifice on performance of plasma synthetic jet actuator

“…When the discharge location moves from the cavity bottom towards the actuator exit, jet duration time decreases but strong temporal oscillations of the exit velocity are observed, possibly due to the enhanced shock wave reflections (Zhang et al 2015). Electrode shape can affect the impedance matching of the discharge circuit, and a large length-to-diameter ratio of electrodes results in a high cut-off working frequency (Popkin et al 2013b). As the exit diameter increases, an increase of the peak jet velocity is observed while the jet duration time drops.…”

Plasma Synthetic Jet Actuators for Active Flow Control

“…Their dimensions and shapes can influence not only the device efficiency, but also the discharge stability (e.g., occurence of misfires). A first investigation on the influence of electrodes shape and size was carried out by Haack et al in [10], where electrodes with two different tip shapes (cylindrical and truncated cone) are tested in pure tungsten and tungsten alloys (lanthanated, ceriated, zirconated and a copper/tungsten alloy known as Elkonite). They found out that the cylindrical tip shape for both electrodes (anode and cathode) produced the best actuator performance with a low misfire percentage, which can be attributed to the relatively higher electric field at its corners.…”

“…For all the materials tested, only copper/tungsten electrodes did not exhibit a good survivability, largely because the addition of copper incurred a significant alteration of the tip shape which lead to noticeable misfires in several burst sequences. Moreover, Haack et al [10] also studied how the electrode diameter can affect the frequency response of the actuator, when the same material and tip shape were used. Results indicated that the cut-off frequency increases monotonically with the electrode length-to-diameter ratio.…”

“…ca (10) where ρ, T and p are the density, temperature and pressure, respectively. Subscripts associated to these symbols indicate the location where these parameters are evaluated, e.g., ca-actuator cavity, e-nozzle exit.…”

“…In this case, the discharge occurs only when the trigger voltage is activated (O(kV)), ionizing the air electrode gap and allowing the capacitor energy to be released between the main electrodes (few hundreds volts discharge) [9]. Nowadays, the power supply system has moved from an external trigger to a pseudo-series trigger [10]. Namely, the third trigger electrode has been removed, and both the trigger and main discharge are integrated into the anode.…”