Effect of oil-based emulsion on air bubbles in the spray sheet produced through the air-induction nozzle

The air-induction spray featured by air bubbles involved in the spray sheet has attracted great attention in applications of agricultural spray due to its advantages of alleviating spray drift and promoting deposition. The objective of the presented study is to deepen the understanding of the mechanism of the air-induction spray through elucidating the effect of sprayed liquid on characteristics of air bubbles in the spray sheet.

The air bubbles with relatively large sizes are stable for a long time span. As velocity of the water spray increases from 6.85 m s^-1 to 17.87 m s^-1 , average size of the air bubbles decreases from 383.21 μm to 236.47 μm. With the introduction of organosilicone surfactant, the surface tension of the sprayed liquid decreases from 67.38 mN m^-1 to 31.32 mN m^-1 ; accordingly, average size of the bubbles decreases from 383.21 μm to 160.9 μm. Compared to aqueous solutions spray, the oil-based emulsion spray is responsible for relatively small average size of air bubbles as the surface tension and spray velocity are respectively similar.

Low drainage rate of the bubble lamella contributes to high stability of large air bubbles. The decrease of the average size of air bubbles is responsible for small volumetric median diameter of oil-based emulsion spray compared with water spray. Besides the increase of the spray velocity and the decrease of the surface tension, the Marangoni effect caused by dynamics of oil droplets at air-liquid interface also contributes to the decrease of average size of air bubbles. © 2022 Society of Chemical Industry.