Assessment of a 3S rotary atomizer

Spinning disc sprayers were first introduced to control cotton pests and diseases. These atomizers were recognized for their production of a uniform droplet size spectrum than conventional nozzles. They have proved to be the most successful way of delivering pesticides in the form of Controlled Droplet Application (CDA) at very low volume application. But they were almost abandoned since the years of 1990 for high and medium volume application. Their use was found inefficient in arable crops such as cereals due to the use of inappropriate application rate and problem of penetration of spray in cereal canopies. However, these spray generators may be the best solution when the spray was to be targeted to a small weed with hydrophobic leaf surface where adhesion in the impact is essential for treatment efficiency while minimizing drift and splash thanks to reduced droplet span. In this study, aiming to maximize the control of black grass in cereals, characterization of the droplet size spectra was performed to predict the trajectory droplet and estimate the number that will hit the targeted surface. So, a CDA Micromax Ltd rotary atomizer 3S was operated at different rotation speeds (2000, 3500 and 5000 rpm), flow rates and pressures. A camera X stream -3S which allows the acquisition images in PIV mode, connected to a led lightening set at double mode exposure, were placed in front of the edge of the disc on a spray bench. Images were treated through a laboratory developed Matlab code for Particle Tracking Velocimetry Sizing. Droplets speeds according to diameters were extracted. Droplets cumulative volume according to diameters was also obtained. As the flow rate rose, the volume median diameter (VMD) increased. On the other hand, the VMD decreased as the rotation speed increased. Satellites droplets were observed when the atomizer was operating at a disc speed of 2000 rpm. For each flow rate corresponding to a drop size VMD, the number of droplets/cm2 that will affect pesticide coverage was calculated. Thus, the number of droplets that will effectively adhere depend on their impact at the moment of their arrival to the surface target.