Droplet size classifications for hollow-cone nozzles manipulated with two different PWM valves

Abstract

Implementation of PWM-controlled hollow-cone nozzles in orchard sprayers is the optimal solution to achieve variable-rate applications; however, there is still little information on the droplet size distribution and spray quality for these nozzles. Droplet spectra were investigated for hollow-cone nozzles with five flow capacities (D2-DC25, D2-DC45, D4-DC25, D4-DC45, D5-DC25) connected to two different commercial 10 Hz-PWM valves under laboratory conditions. Other variables for the droplet size measurements included three operating pressures (276, 552, 827 kPa) and ten duty cycles (DUCs) ranging from 10% to 100% at 10% intervals. Volumetric diameters (DV0.1, DV0.5, DV0.9) were determined with a particle/droplet image analytical laser system and were used to calculate the overall droplet size distributions. Additional assays were conducted following the ASABE standard S572.3 to classify the corresponding droplet sizes. The classification of droplet sizes based on the ASABE standard illustrated that the same flow capacity nozzle controlled with two different PWM valves generally produced similar droplet spectrum classifications. As a result, the information established from the tests would be implemented in the future precision variable-rate spray system designs using PWM valves. © 2022 ASABE. All Rights Reserved.Postprint (published version