Spray Droplet Size in Liquid Sheets Containing Surfactants and Oil Emulsions

IAROSLAV MAKHNENKO, Long Nguyen, Cari Dutcher, Christopher J. Hogan, Elizabeth Alonzi, Christine Colby, Steven Fredericks, University of Minnesota

     Abstract Number: 473
     Working Group: Control and Mitigation Technology

Abstract
Droplet atomization is a common process in everyday life with applications in agriculture, drug administration, printing, and painting. For agriculture purposes, small droplets generated from liquid sheets are needed to enhance coverage of agricultural sprays, but not so small that they cause drift of the sprayed pesticides. Spray drift can cause the deposition of chemicals to undesired areas with a negative impact on livestock, ecosystems, and human health. In this work, different factors influencing spray break-up and droplet size distributions are discussed. Herein we experimentally measure the droplet size distribution of sprays from agricultural spray nozzles containing surfactants and oil emulsions using a wind tunnel. We identified the influence on spray volume fraction below 150 μm and on the volume median diameter, which are correlated with the spray drift risk and deposition, respectively. In addition to the wind tunnel experiments, we study uptake and penetration of spray chemicals on the surface of a leaf. It includes measurements with varied humidity to study the phase state of a droplet under different conditions, and fluorescent microscopy to observe the uptake and spreading of a droplet. The results of this work will help to understand the factors affecting a droplet size during a spraying process, towards increased efficacy of spraying pesticides.