Non-intrusive Acoustic Measurement of High Cycle Fatigue in Gas Turbine Engines

Techsburg proposes to explore and demonstrate an innovative approach for non-intrusive sensing of rotor blade vibrations using microphone pressure sensors imbedded into the casing of a gas turbine aero-engine. This non-intrusive sensing strategy is intended to serve an engine health management system capable of monitoring blade material conditions as it pertains to high cycle fatigue (HCF). In this Phase I work, an array of microphones is to be distributed throughout the engine casing to detect the acoustic pressure waves elicited by forced blade vibrations. A proof-of-concept experiment will be performed at the Stage Matching Investigation (SMI) rig at the Compressor Aerodynamic Research Laboratory (CARL) of AFRL in Dayton, Ohio. The casing-mounted microphone signals will be correlated to the on-blade strain measurements in order to develop this non-intrusive blade vibration sensing technique. Phased-array signal processing techniques will be used to provide a high SNR indicator of the rotor blade vibration amplitudes. Then in Phase II of this work, an array of low-cost micro-electromechanical systems (MEMS) pressure sensors will be used to demonstrate a more flight-worthy software/hardware package capable of detecting blade vibrations real-time.