Thermographic Phosphor Thermometry for Temperature Measurement of an Impinging Supersonic Jet

Thermographic Phosphor Thermometry (TPT) is a non-invasive optical temperature measurement technique that offers significant advantages for heat transfer investigations including high spatial resolution and accuracy, compared to traditional methods such as thermochromic liquid crystal and infrared cameras. TPT utilizes ceramic phosphors doped with rare-earth or transition-metal ions. While the host material is optically inactive, the doping ions serve as luminescent activators, absorbing specific excitation wavelengths and emitting photons at longer wavelengths. The emitted light’s spectral characteristics and lifetime decay depend strongly on temperature, making TPT particularly suited for high-resolution thermal mapping. In this study, several phosphor particles including La₂O₂S:Eu, BAM:Eu, YAG:Dy, YAG:Cr, and MFG:Mn, were excited using a 385 nm ultraviolet LED and their emission spectra were characterized using a spectrometer. MFG:Mn phosphors exhibited prominent emission peaks at 632 nm and 658 nm; the stronger peak at 658 nm was selected for temperature measurements. Calibration of phosphor lifetimes will be conducted over temperatures ranging from 25°C to 350°C to establish a lifetime-temperature calibration curve, where lifetime decreases with increasing temperature. These results lay the groundwork for precise temperature measurements of impinging supersonic jet flows.