Surface thermometry using laser-induced phosphorescence applied in the afterburner of an aircraft turbofan engine

In the present work surface thermometry using a method based on the spectroscopy of inorganic luminescent material has been applied in a full-size aircraft jet engine. The technique utilizes laser-induced emission from thermographic phosphors for, non-intrusive, remote temperature diagnostics in combustion applications with high sensitivity and accuracy. In the present application the laser-induced phosphorescence technique has proven its applicability even in the extremely harsh environment prevailing next to a jet engine operating at full load. The measurement object, Volvo RM12, is based on the General Electric F404 engine, from which it has been developed to meet single-engine operating criteria and achieve higher performance. A phosphor material having suitable temperature sensitivity in the expected temperature range was applied to the surface of interest on the flameholder of the engine afterburner. Phosphorescence radiation was generated using the forth harmonic (266 nm) from a pulsed Nd:YAG laser as an excitation source. The resulting signal was detected with a photo multiple tube (PMT). Phosphorescence lifetime decay curves were recorded at various load of the engine, including use of the afterburner. By analyzing the lifetime decay, the temperature data was acquired through implementation of a regression equation extracted from well-defined calibration measurements on the phosphor used.