Advanced Fiber Optical Sensor and Instrumentation for Power Generation Industrial Monitoring and Diagnostics

Temperature measurement in an extremely harsh environment, such as in a coal gasifier and gas turbine, presents significant challenges to any conventional temperature sensing technology, including thermocouples, IR camera, pyrometer, and blackbody radiation measuring methods. The commonly used fiber Bragg grating (FBG)-based temperature sensors have many advantages, making them very successful in structural health monitoring application. However, conventional FBGs have poor thermal stability and survivability when environmental temperature is beyond 500 degrees C. A band-gap engineering method has been used to transform amorphous fiber material into tetrahedral dominated microstructures, and the mass density modulated grating structure has shown the same fundamental characteristics as conventional FBG but the tetrahedral dominated fiber material enables such grating structure more tolerable to extremely temperature without losing structure integrity. The developed tetrahedral fiber Bragg grating (TFBG) have been prototyped for coal gasification radial and axial distributed temperature measurements. The field validations have demonstrated these TFBG sensors can provide reliable temperature measurement under 1200 degrees C harsh conditions.