Recent studies have shown that thermographic\nphosphor particles are suitable tracers for simultaneous\ntemperature and velocity imaging in gas flows. For the\ndevelopment of this thermographic particle image velocimetry\ntechnique, the choice of phosphor is a key consideration\nand new phosphor materials need to be identified and\ntheir luminescence properties thoroughly characterised.\nThis paper describes a method for investigating phosphor\nparticles for gas thermometry. The method consists of performing\nspectroscopic experiments on particles dispersed\nin the gas, while simultaneously measuring the number\ndensity of tracer particles using a particle counting system,\nwhich is based on high-resolution Mie-scattering images.\nThe measurement of the seeding density allows a direct\ncomparison of different phosphors on a ââ?¬Å?per particleââ?¬Â basis\nand estimation of the effect of the particles on the gas thermal\nproperties. The effect of parameters such as the excitation\nfluence, gas composition and temperature on the luminescence\nemission intensity can be studied independently\nof the seeding density. As a demonstration, this system is\nused to investigate micron-size BAM:Eu2+ particles. The\nnecessary seeding density for precise temperature measurements\nis determined, and a nonlinear dependence of the\nluminescence emission intensity on the excitation fluence\nis identified.
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