Optical Damage Sensors for Automated On-Wing Engine Airfoil Inspection

Two optical methods are proposed for the detection of a range of types of damage on coated and uncoated airfoils in advanced gas turbines, by means of borescope inspection of on-wing parts. The techniques are based on low coherence interferometry and luminescence spectroscopy. The Phase I work plan consists of a demonstration of the measurement capabilities, an analysis of critical components and feasible operating envelope, and a detailed Phase II design and development strategy. BENEFIT: The proposed instrumentation provides a significant advance over currently employed visual inspection of gas turbine airfoils. For instance, with thermal barrier coatings (TBCs), these techniques allow the detection and quantification of incipient spalls, delamination, and changes in TBC porosity which typically go unnoticed with visual inspection methods. The proposed methods are well suited for use with borescopes and thus provide a large potential to be developed into commercial optical diagnostics instruments for use during maintenance and inspection of advanced gas turbines.