Piezoelectric ring-stack actuator design for high-frequency valve

This paper presents a fundamental non-contact valve design developed by integrating a ring-stack piezoelectric actuator into a converging nozzle design to impart harmonic flow. The paper also outlines the governing equations as well as limiting factors that constrain the design and operating performance. The converging nozzle design achieves choked flow at the valve exit when the nozzle is fully open. Valve actuation centers around piezoelectric ring stacks: the piezoelectric stack is fixed within the valve on one end to the base plate and has a conical nozzle tip attached to the opposite end of the stack. When the stack fully displaces to its maximum length, the nozzle tip is in the closed position where minimal flow passes through the valve exit. The flow area between the nozzle tip and casing wall achieves maximum mass flow rate when the piezoelectric stack is at minimum length. The change in flow cross-sectional area due to the piezoelectric stack displacement generates a change in mass flow rate through the valve. Due to the small-scale displacement of piezoelectric stacks, different angles of the nozzle cone and casing are required to achieve a greater desired mass flow rate. This model is adjustable to accommodate various piezoelectric stack sizes and displacements or to alter the exit mass flow rate to best suit a particular application.