DROPLET SPECTRA AND WIND TUNNEL EVALUATION OF VENTURI AND PRE-ORIFICE NOZZLES

Abstract

Small- to medium-size droplets are desirable when applying insecticides and fungicides because they provide better penetration into the canopy and better coverage than larger sizes. However, small droplets can drift long distances. Several agricultural nozzle manufacturers have recently introduced so-called “low-drift” nozzles. Although manufacturers of low-drift nozzles claim these nozzles are considerably more effective in reducing spray drift than standard flat-fan nozzles, no independent data are available to support their claim. The objective of this study was to determine the effectiveness of two low-drift nozzles (TurboDrop® and Turbo TeeJet®) in reducing drift. The TurboDrop nozzle design incorporates a venturi air intake port and a pre-orifice chamber while the Turbo TeeJet nozzle design includes only a pre-orifice chamber. Nozzle evaluations were accomplished by measuring droplet sizes with a laser particle sizer and deposition distances of droplets in a wind tunnel (5 m/s). Data from measurements obtained with the low-drift nozzles were compared to data from a standard flat-fan nozzle. The low-drift nozzles produced fewer drift prone droplets and significantly lower downwind airborne deposits than the standard flat-fan nozzle (XR). In general, droplet size measurements taken along the long axis of the spray patterns showed less variation in volume median diameters for the XR and Turbo TeeJet (TT) nozzles than for the TurboDrop (TD) nozzles. The TD nozzles produced lower downwind deposits than TT nozzles operated at similar pressures (276 kPa); however, a larger orifice TT nozzle operated at a lower pressure (176 kPa) produced significantly lower downwind airborne deposits than the TD nozzle operated at 276 kPa. Covering or restricting the venturi air intake port on the TD nozzle increased nozzle output but had little impact on the overall droplet spectrum and downwind drift.