Scattering referenced aerosol phosphor thermometry

Abstract

This work presents a new thermographic phosphor particle-based gas thermometry technique that utilizes the ratio of temperature-dependent luminescence intensity and the temperature-insensitive elastic Mie scattering from phosphor particles seeded into the gas. This method has the potential for high temperature sensitivity. However, the large range of particle sizes typical of thermographic phosphors results in additional uncertainty in the measured ratio and temperature. The uncertainty in the intensity ratio is measured as a function of phosphor seeding density for the phosphor Ce:LuAG. The added uncertainty in the single-shot ratio measurements, assumed to be due to the non-uniform particle size distribution (PSD), was estimated to range from 20% for a seeding density of 40 mm−3 to 10% at 210 mm−3. Measurements at heated jet exit temperatures of 750 K and 820 K revealed that, even with the added ratio uncertainty, single-shot temperature precisions better than 2% (<15 K) were achieved with seeding densities less than 150 mm−3. By combining ratio precision and temperature sensitivity measurements, it was estimated that the technique is capable of single-shot temperature precision better than 4% from 670 K to 1000 K, and better than 1.5% from 800 K to 900 K, for a seeding density of 300 mm−3. Measurements are limited to temperatures greater than approximately 600 K for Ce:LuAG due to low temperature sensitivity and a double-valued ratio below this temperature. These results demonstrate the potential of this new strategy to advance the state-of-the-art for APT measurements.