Flow-Blurring and Air-Assisted Atomization of Newtonian and Non-Newtonian Liquids

A comprehensive study on Flow-Focusing/Flow-Blurring (FF/FB) atomizers is presented in this study. A transparent FF/FB atomizer is introduced in this work to aid in the characterization of sprays emitting from both of the atomizer’s regimes. Newtonian and non-Newtonian liquids were tested over a wide range of operating conditions and laser diagnostics were employed to unveil the resulting structures and salient features of the sprays. Direct imaging of the atomizer’s liquid tube tip region enabled identification of the onset of the atomizer’s regime transition at different liquid tube recesses and over a wide range of conditions. New regime transition maps for FF/FB atomizers have been created that are function of ALR, Weber number, momentum flux ratio and liquid Re, and can be employed to identify the operating regime of atomizers and the controlling parameters for transition. Spray droplet size and flow-field measurements using a PDPA/LDV setup were obtained and have enabled identification of unique flow features that characterize the FF and FB regimes, of importance is the shown dependence of the resulting droplet size on the operating Weber number for both regimes, and the trend of decreasing difference in droplet size between the two regimes as the Weber number increased. The spray morphology of Newtonian and non-Newtonian liquids was also investigated. The FF regime was found to behave similarly to air-blast atomizers when operating with non-Newtonian liquids, it had an advantage though in the atomization of Newtonian liquids. The FB regime demonstrated the ability to always generate droplets immediately as the spray exited the atomizer when operating with Newtonian liquids. However, non-Newtonian liquids have proven to be difficult to atomize in the FB regime where the liquid separated into multiple streams and only broke up at far downstream locations