Ultra High Temperature Fiber Optic Thermometer

G. Srinivas
TDA Research Inc, United States

Keywords: fiber optic, selective emitter, jet engine, exhaust gas temperature

Jet engines are operating at higher temperatures to improve efficiency and performance, but measuring the exhaust gas temperature (EGT), a critical parameter for evaluating the engine has not kept pace. Thermocouples that are rated at a high enough temperature have very weak signals (which can be drowned out by electromagnetic interference) or cannot be exposed to oxidizing environments. Any sensor must be extremely rugged and able to operate at temperatures greater than 1600oC while withstanding the vibration of the engine and mechanical stresses imparted by the gas flow. Other high temperature sensing techniques are not rugged enough, too expensive, or too complicated to effectively measure exhaust gas temperature in real world conditions. TDA has developed a high temperature fiber optic thermometer that can reliably measure temperature from 300oC–1800oC. TDA’s technology is insensitive to electromagnetic interference, oxidizing environments, or corrosive environments. TDA's sensor uses sapphire fibers and a spectrally selective emitter as the sensing element. Since we measure temperature by using a ratio of intensities at multiple emission peaks, instead of a single peak, the sensor produces a high signal to noise ratio, even in adverse conditions such as high vibrations or significant blackbody radiation from outside sources.