Numerical simulation of spray ejection from a nozzle for herbicide application: Evaporation and binary collision models

Abstract

The numerical simulation of water spray ejected from HARDI™ ISO F110 03 flat fan nozzle has been performed in this work. The simulation models of ejection and trajectory of liquid droplets proposed in previous study are used for obtained the diameters distribution and velocity of liquid particles and the collision drops phenomena into the spraying fat fan. The aim of this work is take into account both, the collision drops by changing the surface tension and evaporation phenomena using a binary collision and evaporation models. To validate the evaporation model, numerical simulation of water droplet ejection at 293 Kelvin degree were performed and their results has been compared with experimental data published. A total of 9 simulations, varying the meteorological conditions and recording 40 drops of diameters approximate to 100 μm and 200 μm has been performed. For the binary droplet collision, the surface tension of water at 278 Kelvin and 293 Kelvin was considered in order to vary its surface tension. Also, water at 293 Kelvin with different surface tension was considered in order to represent mixtures with surfactants. Collision boxes were implemented in order to determinate the impact coefficient. Four outcomes were identified: (a) coalescence, (b) reflexive separation, (c) stretching separation, (d) bounce. The generation of satellite droplets in the reflexive separation and stretching processes increases the drift risk when the product is applied. The alternative that show a better option to minimize the drift risk is water at 278 Kelvin. Additionally, it was determined that considering the processes of evaporation and collision of droplets, ejecting droplets with an average diameter of 350 μm, by obtaining a good fit (coefficient of determination R2>0.96) between the droplet distribution curve and the volume of experimental measurement.