Microphone Sensing of Fan Face Distortion

The use of Boundary Layer Ingesting (BLI) embedded engines offers a significant benefit to the performance of Blended Wing Body (BWB) aircraft in the form of decreased ram drag and increased propulsive efficiency. However, in order to realize the benefits of embedded engines, effective serpentine inlets must be designed to properly ingest the incoming boundary layer without creating excessive fan face distortion. The concept of using jet-type vortex generator arrays to manage the secondary flows in BLI serpentine inlets has been proven to be quite effective. However, in order to implement these flow control techniques in an active control system, an accurate and non-intrusive inlet distortion measurement technique must be available. The team of Techsburg, Inc. and AVEC, Inc. are proposing a novel, non-intrusive microphone based, inlet distortion sensing package that offers the potential to provide this capability. This technology will be tested in Techsburg’s transonic, variable Reynolds number, BLI inlet test facility. As a final demonstration of the technology, the sensors will be incorporated into a closed-loop flow control scheme. In addition to the microphone sensors, the control package will include a PID controller and an array of vortex generator jets previously developed by Techsburg to control distortion.