Supercontinuum-illumination for long-working-distance microscopic imaging of air-liquid mixed sprays in the near-nozzle region

We demonstrate the optical diagnosis of air-liquid mixed sprays in the near-nozzle region using the supercontinuum (SC)-illumination long-working-distance microscopic imaging method, enabling the imaging of microdroplets, ligament structures, and cavities. In addition, SC-illumination long-working-distance microscopic imaging effectively suppresses speckles and reveals the ligament structures in the sprays more accurately. Finally, analysis of the droplet size distribution of the sprays under different air and liquid flow rates indicates that SC-illumination long-working-distance microscopic imaging offers several advantages for studying spray dynamics at the small structure level.