Measuring the temperature of a rapidly evaporating water droplet by Planar Laser Induced Fluorescence

In this paper, we present the experimental research into the unsteady temperature fields of an evaporating water droplet with a 1-2 mm initial radius attached to a holder in a flow of air heated up to 1,000 degrees C. The limitations of Planar Laser Induced Fluorescence are established. We identify four distinct stages of droplet evaporation, in which the use and calibration of Planar Laser Induced Fluorescence differ significantly. Changes in the dye concentration in the droplet are found to result from the dye evaporation from the free surface of the droplet and its sedimentation onto the holder. A correction factor is introduced, based on the experimental results and dependent on a number of effects discussed. The factor is used to adjust the experimental measurements made via Planar Laser Induced Fluorescence and to obtain the reliable temperature fields of a rapidly evaporating water droplet. (C) 2018 Elsevier Ltd. All rights reserved.