An experimental investigation of luminescence lifetime thermometry for high temperature engine components using coatings of YAG:DY AND YAG:TM

Experiments were conducted to evaluate the performance of a thermographic phosphor thermometry system for measuring temperatures of engine hot section components, such as turbine blades and vanes. Two vanes, one coated with YAG:Dy and the other with YAG:Tm, both applied on top of a thermal barrier coating (TBC), were tested. Measurements of laser-induced luminescence lifetime were obtained from both vanes at room temperature, and from the YAG:Dy vane supported in the exhaust of an afterburning turbine engine. The measured luminescence lifetime was found to vary in a systematic way with signal level for both phosphor coatings. This behavior was attributed to saturation effects of the detector. Estimated temperatures of the YAG:Dy-coated vane at afterburning conditions were in the neighborhood of 1250 °C. Signal levels were found to be sufficient to enable a precision of 6 °C at 1050 °C, extrapolated to 3 °C at 1250 °C. Background levels at full afterburner were significant, but manageable using narrowband spectral filtering of the collected luminescence. These findings indicate that a thermometry system for engine components at high temperatures is feasible using at least one, and possibly either, of these coatings.