A piezoelectric-based, high-frequency flow valve for non-contact excitation of turbomachinery for flutter boundary mapping

A key indicator of flutter risk in turbomachinery is aeromechanical damping, which decreases when approaching a flutter boundary. Current flutter testing methods require flutter boundary crossing and only provide binary flutter/no flutter data. Aeromechanical Identification Methodology (AIM) allows damping measurements to be collected during operation. These measurements allow identification of flutter boundaries without requiring the test article to encounter flutter. This approach is safer and enables AIM operation over a wider range of conditions. This approach would significantly improve present flutter testing; however, current available actuators’ low-frequency capabilities have limited AIM’s applicability to commercial fans. AIM utilizes noncontact actuation, avoiding concerns associated with on-blade actuation, such as added structural mass or wiring through a slip ring. A proposed piezoelectric-based, high-frequency flow valve presents a non-contact actuation method by injecting oscillatory flow during engine testing, offering a solution to the previously limited data range. Fluid supplied to the valve imparts a compressive load to the piezoelectric stack. Applied voltage actuates the stack, driving a pintle to modulate the cross section of a choke point and producing an oscillatory mass flow injection to the turbomachinery flow. A secondary inner volume offers a method to adjust the pressure difference across the pintle head, which in turn allows greater control over the displacement range and associated injected mass flow variation. This more extensive range of achievable injected mass flow rates and operating frequencies enables mapping flutter boundaries across a broader range of structures and operating conditions.