Droplet Sizing Based on Mie Scattering by Out-of-Focus Imaging

Abstract

The global aim of this study is to measure droplet diameters by a technique based on the evaluation of the number of fringes on an out-of-focus plane. This technique is performed on a water jet with laser light scattering at collecting angle of 90° to verify its validity. The final goal of this work will be to apply this technique in a Micro-Combustor Chamber with a LOX/GH2 spray to measure simultaneously the size and the velocity of droplets. In this report, I first remind theoretical basements of the Mie scattering technique in order to obtain a clear expression of the droplet diameter by using the number of fringes and the geometrical parameters. The droplet sizing method is tested on two different water jets with several cameras, for droplets between about 10 to 120µm. This technique has demonstrated the usefulness of the Mie scattering method for these types of experiments. Measurements made on water drops produced by both droplet generators yielded a reasonable range size.