Impact of Plugged Venturi Nozzle Air-Inclusion Ports on Droplet-Size Distribution

Concern about pesticide drift has increased dramatically in recent years. An emphasis on increasing spray droplet size to mitigate off-target particle movement has occurred in response to this concern. Venturi nozzles were designed to create coarser droplets by entraining air within the spray solution in the nozzle body. In field applications, dirt, fertilizer, and other debris can plug air-inclusion ports. The objective of our research was to identify the impact of plugged air-inclusion ports on the droplet-size distribution of multiple venturi nozzles. The study was conducted using the low-speed wind tunnel at the Pesticide Application Technology Laboratory in North Platte, NE. Droplet-size distributions for five venturi nozzles and two orifice sizes (Air Induction [AI11004 and AI11006], Air Induction Extended Range [AIXR11004 and AIXR11006], Turbo TeeJet Induction [TTI11004 and TTI11006], Turbo Drop [TDXL11004 and TDXL11006], and Ultra Lo-Drift [ULD12004 and ULD12006]) were measured in combination with plugged or unobstructed air-inclusion ports, providing 28 total treatments. Measurements were made using a Sympatec HELOS-VARIO/KR laser diffraction system while testing water sprayed at 276 kPa. Similar patterns in droplet-size distribution within nozzles were observed across orifice sizes. When air-inclusion ports were plugged, the D_v0.1, D_v0.5, and D_v0.9 decreased for the AI and TDXL nozzles, remained relatively unchanged for the AIXR and ULD nozzles, and increased for the TTI nozzle. In addition, the percentage of fines less than 150 µm increased for the AI and TDXL nozzles, remained relatively unchanged for the AIXR and ULD nozzles, and decreased for the TTI nozzle when air-inclusion ports were plugged. This research helps to better understand the drift mitigation implications if debris were to plug venturi nozzle air-inclusion ports.