The effect of oil-in-water emulsion pesticide on the evolution of liquid sheet rim disintegration and the spraying distribution

Abstract

Oil-based emulsions often used as agricultural chemical formulations to control pests and weeds. The instability of emulsion spray is an important challenge. In this work, the effects of liquid sheet rim disintegration on spray angle and spraying distribution were studied by visualization method. The results show that the addition of emulsion change the way of rim disintegration and this change may be responsible for the improvement of spray angle and spraying distribution uniformity compared with water spray. In emulsion spray, the typical feature of rim disintegration is the asymmetric “half-moon” shaped holes, which leads to earlier disintegration at the edge of the liquid sheet. The hole coalescence at the rim of liquid sheet may be the reason for the increase of spray angle, because it divides the liquid sheet into small liquid masses and breaks the inward contraction trend of the cohesive attraction of liquid mass. Only 0.02% addition of emulsion, the spray angle could be increased by 8°, the typical liquid sheet breakup length (typical length) and the liquid sheet rim breakup length (rim length) from 23.297 mm to 18.609 mm reduce to 16.3 mm and 9.099 mm, and the spraying distribution curve become more uniform. In addition, the effects of spray structure on spraying distribution characteristics under different concentrations and spray pressures are also discussed. This study could provide a reference for the optimal use of pesticide formulations in the field, the reduction of pesticide waste and environmental pollution, and the establishment of atomization and fragmentation models.