Fiber-sensor design for turbine engines*

Determination of blade temperatures in the high-speed and turbulent environment of a turbine engine is difficult using standard pyrometry techniques because of the presence of high-temperature flame and the reflective nature of the inspection surfaces. A technique utilizing thermographic phosphor compounds bonded to engine vanes and turbine blades is presented that mitigates the negative effects of blackbody radiation while potentially allowing near real-time acquisition of blade temperature information. Specialized single and dual fiber-optic probes were designed to interrogate both fixed and rotating surfaces by delivering ultraviolet light from a quadrupled Nd:YAG (266 nm) laser to phosphor coatings consisting of Y2O3:Eu, YVO4:Eu, and YAG:Th ceramic compounds. This technique utilizes the temperature-dependent fluorescent emission of a ceramic phosphor coating to discern the temperature of the interrogated surface. By using these methods, surface temperature measurements to 1200°C are achievable in the combustion environment.