Viability of Fiber Optic Temperature Sensors Embedded Within Engine-Scale Turbine Blades

Abstract Accurate predictions of the external and internal temperature distributions of a gas turbine blade are essential to optimizing cooling systems and ensuring blade integrity. Small temperature variations can significantly affect the stress field and hence blade life, influencing the turbine operating cost. While established methods exist for external surfaces, few capture the temperature distribution within the internal structure, both for engine parts and components used in research test facilities. Due to the small sizes and complex internal geometries of blades, optical access is limited, and millimeter-scale spatial resolution is difficult to obtain. This project investigates the viability of embedding fiber Bragg gratings (FBGs) within engine-scale, cooled turbine blades in the Oxford High Temperature Linear Cascade (HTLC). Given their minimally invasive nature, potential for multiplexing, and resilience in harsh conditions, FBGs present an opportunity to capture detailed temperature data for research or in-situ health monitoring. Each FBG reflects a certain wavelength of light, which is sensitive to changes in strain and temperature. A polyimide-coated silica fiber with a diameter of 0.15 mm can include many FBGs along its length, providing measurements of high spatial resolution. This investigation explores the routing of fibers through small bend radii and the use of FBGs to measure temperature in metal test pieces. Following this study, instrumentation of a cooled, engine-scale blade with FBGs will be undertaken in the HTLC.