An investigation into laser diagnostic technique of liquid droplets. I - Measurements in high temperature streams. II Measurement of evaporation rate constant in hot spray

A particle analyzer based on the Fraunhofer diffraction theory and a novel laser diffraction technique have been applied to the study of the local characteristics of spray droplets vaporizing in a stream of hot gas. The results for the former technique indicate that changes in the mean diameter and the size distribution are given by a change in the relative signal value. The spray angle widens during flash boiling and the mean diameter decreases by one-half to one-third. The laser technique was used to predict the evaporation rate constant by comparing the detected relative light energy with the total light energy in the spray. The evaporation constant for ethanol cloud spray was measured by this method and the results agree with published ones. It is confirmed that the outer part of the spray has a larger limited evaporation rate constant than the inner part.