Development of Non-intrusive Fluid Thermometry in Air with Temperature-sensitive Particles by Two-gated Method

A non-intrusive fluid thermometry technique using in-house temperature-sensitive particles by means of two-gated method was demonstrated. In the present research, phosphorescence signals were integrated over exposure time that was much longer than the phosphorescence, thus lower frame rate could be used to avoid faster frame rate which would have compromised spatial resolution. Ruthenium-based temperature-sensitive particles were scattered in a heated turbulent jet emanating from a pipe and its phosphorescence was captured by a sCMOS camera in double-frame mode. Calibration function for temperature vs. intensity ratio between 1st and 2nd frame of the double-frame images was generated by two means: static calibration using a sample on a temperature-controlled surface and dynamic calibration using the potential core of the heated jet. Calibration function of the dynamic case was used to convert the raw images to instantaneous thermal captions, and the thermal captions exhibited typical flow characteristics of a heated turbulent pipe jet such as hot potential core, and low-temperature shear layer with fine-scale structures. The average temperature field of the present demonstration agreed well with temperature distribution measured by conventional T-type thermocouple, confirming the accuracy of the technique. Using 95%-confidence level, the uncertainty in temperature was evaluated to be ±4.9°C at the jet temperature of 96.3°C. Future work is to investigate the factors that contribute to the uncertainty to improve accuracy and precision of the technique