Measurements of droplet vaporisation by means of light scattering

We describe how traditional elastic low-angle light scattering techniques (LAELS) can be employed to determine the evaporation rate of droplet arrays. This objective is achieved by measuring simultaneously the droplet size and spacing (from which the droplet speed can be derived) at different axial positions along the droplet path. The analysis shows that both quantities can be determined with good accuracy. The capability of the LAELS technique in performing reliable particle sizing has been tested by comparing experimental values with theoretical predictions. In addition, the method proved to be a valid tool for studying complex interaction phenomena between vaporising droplets, where competing effects between neighbouring droplets may result in a substantial decrease of droplet vaporisation rate when compared to the isolated droplet case. The temporal evolution of four different droplets arrays has been determined and the influence of interdroplet spacing on the vaporisation process correctly predicted.