First assessment of hollow cone nozzles spray patterns and their effects on orchards sprayer distribution profiles.

Single spray nozzle patterns generated by 60 different hollow cone nozzle types and models conventionally used on air-assisted sprayers were examined. Both conventional and air induction hollow cone nozzles produced by different manufacturers (Albuz, ASJ, Lechler and Teejet), featured by different orifice sizes, were tested operating at 5 bar pressure. According to ISO 5682-1 standard the single nozzle spray pattern generated by a hollow cone nozzle has to be evaluated in 3 different nozzle positions in order to enhance eventual spray distribution diagram distortions. Nevertheless, in the standard there is not any indication how to evaluate the obtained results. With the aim to express the evenness of the hollow cone jet produced by each nozzle, a symmetry index, calculated on the basis of the spray pattern values registered, was used. Single nozzle diagrams were expressed in % values of the total flow rate so to be able to compare nozzles featured by different flow rates. Results pointed out differences between the single nozzle spray profiles produced by nozzles of the same set having different sizes and also differences between nozzle spray patterns produced by conventional hollow cone nozzles with respect to those produced by air induction ones. These differences have consequences on the overall vertical profile of an air-assisted sprayer, therefore must be considered for a correct sprayer calibration when changing nozzles sets on the machine. A “shape” nozzle profile index was therefore studied to characterize the different nozzles families.