Aeropropulsion system performance improvements are becoming increasingly dependent on the use of control technologies. As aeropropulsion engines evolve from rigid mechanical designs to adaptable systems, the need for new, embeddable sensors and actuators becomes critical. The variable-frequency fluidic actuator is a new device developed at the NASA Glenn Research Center that could be built into the components of an engine, thereby enabling advanced technologies known as active flow control.
Flow control is the technology of manipulating the aerodynamic flow over a surface, such as a wing, to enhance its ability to produce lift or to reduce the drag force, especially under severe operating conditions. This has been an area of basic research for many years. In an airframe, flow control is important because it affects the aircraft’s operability, maneuverability, and fuel consumption. In a turbine engine, there are similar concerns because the many small airfoils in the engine must operate over a large range of flow conditions. Only in recent years have these flow-control concepts been extended to the internal workings of a turbine engine.
Research on air-injection flow control in turbomachinery performed at Glenn has reduced loss dramatically because of the mitigation of flow separation on compressor stators. These results, while demonstrating effective means to enhance performance, have also pointed to the lack of suitable actuation devices to effectively implement flow control in the hostile environment inside a jet engine. To further flow-control research and perhaps enable flow control in production engines, Glenn researchers developed the variable-frequency fluidic actuator, an actuation device capable of pulsed injection at variable frequency and duty cycle.
Example of the output flow from a single channel of the actuator.
The actuator produces two highly modulated output flows from a single pressure source. The graph depicts the flow from one channel. The output of the second channel would appear similar but would be 90° out of phase. The device operates on the Coanda effect to switch the source flow to one of the two output channels, thereby forming a stable jet. By applying a very small and momentary force at the control point, as shown in the following drawing, the input flow can be diverted to the opposite channel, where a stable jet is once more formed. Reapplying the momentary control force again results in a switching action at the output. This can be repeated at any frequency and duty cycle up to the acoustic limit of the fluidic channels.
Functional description of the actuator.
The device has been fabricated and tested using miniature, high-speed electromechanical operators to apply the control force as shown in the photograph. An effort is underway to replace the electromechanical operators with an all-electronic operator that will enable further miniaturization and improved high-frequency performance.
Actuator with miniature operators installed.
Find out more about research at the NASA Glenn Research Center: http://www.nasa.gov/glenn
Dennis E. Culley, 216-433-3797, Dennis.E.Culley@nasa.gov
Author: Dennis E. Culley
Headquarters program office: Aeronautics Research Mission Directorate
Programs/projects: Independent Research and Development, Fundamental Aeronautics, Subsonic Fixed Wing
Instrumentation and Controls
Last updated: December 14, 2007
Responsible NASA Official:
Point of contact for NASA Glenn's Research & Technology reports:
Web page curator:
Wyle Information Systems, LLC