Melezhyk O. Enhancement of Dispersivity in Pesticide Spraying

This dissertation is concerned with finding the ways for upgrading economic, operational and environmental parameters of sprayers for plants through enhancement of pesticide dispersivity. The need to better dispersivity in pesticide spraying stems from the efforts to minimize losses of working mixture resulting from droplet bouncing back or slipping off from a treated surface, and to ensure favourable conditions for pesticide penetration into a target object. The author has developed a technique for selection of the form, calculation of dimensions and hydraulic characteristics for a centrifugal nozzle with an optimal swirl chamber. Reliability, long service life and safety of these nozzles are scientifically substantiated. The mathematical simulation method was applied for determination of the effects of wind, humidity and ambient temperatures, and also sprayer speed rates and working mixture pressure and its temperatures on the droplet motion and evaporation intensity inside the spray of the nozzle as well as on droplet precipitation on treated surface. It has been proved that the droplets are subjected to forced precipitation due to the action of a concurrent air flow sucked at the spray root. Axial and radial air propagation velocities in the spray and their effects on formation of the spray spatial structure have been determined. The adequacy of the mathematical model has been verified by reference to calculated and experimental forms of sprays in the nozzle, temperature ranges and droplet propagation rates in the spray. The author has performed a comparative survey of various types of nozzles for pesticide spraying and determined their effects on economic, operational and environmental parameters of sprayers. The nozzles of Ф.03.1.0 model enhance dispersivity in spraying and make it possible to decrease the application rates of pesticides in spraying operations.