Agricultural sprays produced from the atomization of a nozzle-generated liquid sheet produce a wide range of droplet sizes, which impacts crop coverage and spray drift. While the operating conditions and nozzle type are main factors to achieve optimal droplet sizes, the chemical composition of the sprayed mixture also has substantial effect on the droplet size distribution. Particularly, the presence of surfactants and emulsified oil droplets found in agricultural adjuvants can influence droplet sizes, where surfactants tend to decrease droplet sizes and emulsion droplets tend to increase droplet sizes. However, the coupled, mechanistic level understanding of surfactants and emulsified oil droplets together remains mainly unknown. In this study, model spray systems of water, emulsified mineral oil, and surfactants TritonX-100 (water-soluble) and Span 80 (oil-soluble) at varied concentrations are sprayed through a flat-fan nozzle in a low-speed wind tunnel. A laser diffraction setup is used to measure the size distribution of spray droplets as a function of surfactant and oil compositions. The results show a non-monotonic size dependence on surfactant concentration, and importantly that the sprayed droplet sizes are linked with both the oil emulsion size and the aqueous phase dynamic surface tension and surfactant’s critical micelle concentration. The results also show that the oil phase surfactant has no significant impact on the sprayed droplet sizes. While motivated by the agricultural industry, the new insight into surfactant and oil emulsion synergism on sprayed droplet sizes has potential broader applications in multiphase printing, coating, and painting.

中文翻译：

---

含有可溶性表面活性剂和乳化油的水性液体片的喷雾液滴尺寸

由喷嘴产生的液体片雾化产生的农业喷雾产生各种尺寸的液滴，这会影响作物覆盖和喷雾漂移。虽然操作条件和喷嘴类型是实现最佳液滴尺寸的主要因素，但喷涂混合物的化学成分也对液滴尺寸分布产生重大影响。特别是，农用助剂中存在的表面活性剂和乳化油滴会影响液滴尺寸，其中表面活性剂倾向于减小液滴尺寸，而乳液液滴倾向于增大液滴尺寸。然而，对表面活性剂和乳化油滴的耦合、机械层面的理解仍然主要未知。在本研究中，通过低速风洞中的扁扇形喷嘴喷射不同浓度的水、乳化矿物油和表面活性剂 TritonX-100（水溶性）和 Span 80（油溶性）的模型喷雾系统。激光衍射装置用于测量喷雾液滴的尺寸分布作为表面活性剂和油成分的函数。结果表明，尺寸对表面活性剂浓度具有非单调依赖性，重要的是，喷雾液滴尺寸与油乳液尺寸、水相动态表面张力和表面活性剂的临界胶束浓度相关。结果还表明，油相表面活性剂对喷雾液滴尺寸没有显着影响。尽管受到农业产业的推动，对表面活性剂和油乳液对喷雾液滴尺寸的协同作用的新见解在多相印刷、涂料和涂装方面具有更广泛的应用潜力。