The present study focused on the effervescent atomization of oil-in-water emulsions and its influence on
the internal emulsion structure. The impact of atomization conditions and nozzle geometry on an oil-inwater
emulsion with varied viscosity ratio of disperse phase to emulsion was determined. The viscosity
ratio is known as a key factor for the drop breakup in emulsification processes. The results depict that oil
drops are broken up according to emulsification mechanisms during atomization. A maximum breakup
was found for a viscosity ratio between 0.5 and 1. The expected stress dependency of the drop size change
was observed for high viscosity ratios only. Relevance of elongational stress on the drop breakup was proven
with significant drop size change at high viscosity ratios. The viscosity ratio thus allows for an efficient control of oil drop size change in effervescent atomization as the spray characteristics are invariant
to viscosity changes within certain limits.