Temperature measurements of combustible and non-combustible surfaces using laser induced phosphorescence

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In recent years, thermographic phosphors used for surface temperature measurements have been developed to suit combustion applications. Pulsed ultraviolet laser radiation at 266 nm and 7 ns duration was used to excite a thermographic phosphor, Mg 4FGeO 6:Mn, which was adapted to the surface of the investigated material. The laser-induced emission from the phosphor was recorded. A calibration of the phosphorescence lifetime and spectral properties against temperature allowed surface temperature measurements between 298 and 873 K. The techniques were successfully used in a flame spread scenario for two-dimensional measurements of surface temperature on a low-density fiber board. The phosphorescence images were obtained with eight consecutively gated CCD detectors enable pixel by pixel-lifetime evaluation of the phosphorescence by interpolating an exponential–decay curve to the counts of the corresponding pixel positions of the sequential CCD images. The best precision, better than ±5 K, was obtained at these temperatures. The technique was also applied to temperature measurements of decomposing materials in a pyrolysis oven. The material investigated was birch particles. Recent development of the technique has allowed other applications, e.g., to such as engine valve and droplets temperature measurements.