ILASS-Americas 22nd Annual Conference on Liquid Atomization and Spray Systems, Cincinnati, OH, May 2010 Planar Laser Induced Fluorescence (PLIF) Flow Visualization applied to Agricultural Spray Nozzles with Sheet Disintegration; Influence of an Oil-in-Water Emulsion Michael D. Cloeter *1 , Kuide Qin 2 , Pramod Patil 1 , Billy Smith 1 1 The Dow Chemical Company, Core R&D, Fluid Mechanics & Mixing Discipline, Freeport, TX 2 Dow AgroSciences LLC, Crop Protection R&D, Indianapolis, IN Abstract A typical agricultural spray process involves atomizing a liquid stream of diluted pesticide solution through hydraulic spray nozzles that inherently produce a wide spectrum of spray droplet sizes. Finer droplets have higher potential for off-target movement or drift, which is of concern due to their potential impacts on neighboring crops and livestock, sensitive ecological resources, and human health. A factor that has been found to reduce fines production is the addition of an oil phase in the form of an oil-in-water emulsion. The mechanism of the effect is not fully understood. The flow visualization technique Planar Laser Induced Fluorescence (PLIF) is commonly employed for characterization of scalar mixing. PLIF has also been used to characterize sprays. For this study, Rhodamine WT fluorescent dye was mixed into the solution to be sprayed. The laser sheet, aligned vertically, is passed through the exit area of the nozzle causing the droplets to fluoresce. The fluoresced pattern is imaged. For sprays, image pairs are taken on the order of 100 μs apart, thus the displacement and hence velocity vectors of drops can be computed throughout the spray pattern. Additionally, the images are of sufficient quality to study liquid sheet breakup physics. For sprays with sheet breakup, such as many fan-type agricultural sprays, PLIF is effective at measuring the velocity within the spray before, during, and after the sheet disintegration. The motion of surface features on the sheet before disintegration allow the velocity to be calculated in a similar fashion to discrete particles. Traditional Particle Image Velocimetry (PIV) can in principle work as well, however the image quality from light scattered off of the unbroken sheet in PIV was found to be inferior to images from fluoresced light generated within the sheet by PLIF. The method was applied to fan sprays (hydraulic and air-induced) in common use in agricultural applications. Measurements were performed with and without an emulsifiable methylated soybean oil concentrate phase. Velocity profiles were shown to be consistent with patternation data taken via a mechanical collection method. It was shown that the oil phase has a large impact on velocity profile. The effect of the emulsion on liquid sheet breakup physics was elucidated from the PLIF imaging. * Corresponding Author: mcloeter@dow.com