LASER-INDUCED FLUORESCENCE TEMPERATURE SENSOR FOR IN-FLIGHT DROPLETS

Abstract

Laser-induced fluorescence (LIF) is used to develop a noncontact temperature sensor. The noninvasive sensor is sensible, reversible, and reproducible to temperature changes, and can be used as a temperature indicator for in-flight droplets. A calibration curve relating fluorescence emission intensity to temperature of a solution was developed for a mixture of ethanol-pyrene at S mM concentration. The percentage by mass of the mixture is 99.9% ethanol and 0.1% pyrene. The calibration curve was used as a noninvasive sensor to measure temperature of in-flight droplets. The mixture of ethanolpyrene concentration at 5 mM was used as the base fluid to generate droplets of 215 μm. These droplets were atomized at a velocity of 10 m/s. Droplet temperature measurements were achieved at 1.9, 2.9, and 3.9 cm downward from the tip of the atomizer with the aid of the noncontact thermometer. The initial temperatures of the droplets were changed to 50, 40, and 33°C, and the resulting decrease in temperatures was attributed to heat and mass transfer between the droplets and the surrounding environment