A supersonic broadband microjet actuator using piezohydraulic actuation

Abstract

A supersonic piezohydraulic microjet flow control actuator has been developed using a 400-µm-diameter micronozzle capable of producing pulsed microjet flow over a broad frequency range from quasi-static to 1.6 kHz. Such flow control actuators are useful in providing ideal control inputs for controlling flow properties to improve aerodynamic performance, for example, reduce or eliminate flow separation and mitigate noise from propulsion systems and other aircraft components. The design of the piezohydraulic microjet is presented in combination with experimental results to quantify the internal system dynamic characteristics in comparison with the microjet flow. The microjet actuator couples a piezoelectric stack actuator and a hydraulic circuit to amplify the 20-µm stack actuator displacement to an amplitude that is necessary to throttle flow through the 400-µm-diameter micronozzle. Unsteady pressure measurements at the microjet exit are correlated with the piezoelectric stack actuator displacement and voltage input to provide comparisons between the internal electromechanical actuation and external pulsed flow behavior. Phase-conditioned micro-Schlieren imagery is also utilized to quantify the flow field. The results illustrate broadband supersonic pulsed microjet actuation frequencies that approach 1 kHz: frequencies that are much higher than currently achieved with broadband actuators with this control authority.