Atomization and Sprays

ASSESSMENT OF PARAMETERS FOR DISTINGUISHING DROPLET SHAPE IN A SPRAY FIELD USING IMAGE-BASED TECHNIQUES

SINOPSIS

Quantification of droplet shape in a spray field can elucidate several characteristics and mechanisms of the atomization process such as droplet deformation, breakup, and collision. To identify an optimum parameter for accurate quantification of droplet shape using image-based measurement systems, several parameters from different applications are presented in terms of their mathematical definition, calculation procedure, and characteristics. An experimental investigation using a shadowgraph droplet analyzer is also conducted to provide visual evidence of droplet shape in a spray field. The droplets from this data set are classified based on their shape into three categories, namely, spheres, deformed droplets, and ligaments. The capability of the shape parameters in distinguishing between these droplet groups is investigated using a simulation and the collected droplet images. Many of the parameters have insufficient resolution to distinguish between different droplet shapes. A new scaling parameter is applied to each of the parameters to distinguish droplets that are purely convex (spheres and deformed droplets) from those that have concavity (ligaments). From those investigated, an optimum shape parameter is suggested to distinguish the three droplet groups.