Microphone Sensing of Fan Face Distortion

With the recently announced Higher Bypass Ratio Inlet Development (HiBRID) program, the US Air Force has initiated the design of an inlet for high bypass ratio turbofan engines to be embedded in the next generation of mobility aircraft. Due to the challenges of the design, the inlet will likely require some form of active flow control to maintain an acceptably low level of fan face distortion. In order to be effective, any closed loop control system will require a sensing scheme that can accurately measure the level of fan face distortion. It was with this motivation that the team of Techsburg, Inc. and AVEC, Inc. proposed the development of a non-intrusive, microphone based distortion sensor as a Phase I effort to the US Air Force. The result of the Phase I effort confirms the potential of the sensing technology and provides the groundwork for the proposed Phase II effort. In the first year of the proposed Phase II effort, the development of the sensing scheme will continue with sub-scale tests using inlets representative of the technology being developed in the HiBRID program. These tests will be designed to refine both the sensing technology before committing to engine tests in the second year of the proposed effort.