An image feature consolidation technique (IFCT) to capture multi-range droplet size distributions in atomizing liquid sheets

Atomization of an attenuating liquid sheet beyond the breakup point is visualized by shadow imaging. Of interest is the transitional region where the disintegration of the liquid sheet into a spray occurs. This region is characterized by the coexistence of fine droplets and large unbroken ligaments. The large range of size of the droplets, relative to the unbroken ligaments, exacerbates the out-of-focus and resolution issues which are inherent in the optical imaging of sprays. To rectify these, two shadowgrams with different depths of field (DOF) and resolutions are obtained at each area of interest within the spray, using two different optical setups: finer droplets are observed in the shadowgram with shallow DOF and high resolution; and larger particles, mostly unbroken ligaments, are clearly captured in the shadowgram with deep DOF. Then, an image analysis technique is used to extract the spray features visible in each shadowgram, and the data obtained from the two shadowgrams are consolidated into one histogram representing the nearly complete range of droplet sizes within the spray. This Image Feature Consolidation Technique (IFCT) and the resulting droplet size distribution are found to be useful for applications involving developing sprays.