COMPARING DOWNWIND SPRAY DROPLET DEPOSITS OF FOUR FLAT-FAN NOZZLE TYPES MEASURED IN A WIND TUNNEL AND ANALYZED USING DROPLETSCAN. SOFTWARE

Abstract

Wind tunnel experiments were conducted to examine the ability of four flat-fan nozzles designed for herbicideapplications to reduce the downwind movement of spray droplets (drift). The nozzles were compared at 47 and 94 L/ha incrosswind and headwind application scenarios at a constant wind speed of 4.6 m/s. Each nozzle was used at the commonrecommended field operating pressure of 173 kPa for the extended range (XR) flat-fan, 242 kPa for the turbo (TT) flat-fanand the Combo-Jet (DR) flat-fan, and 345 kPa for the venturi (AI) flat-fan. Downwind droplet movement used as an indicatorfor drift was collected on water-sensitive paper (wsp) positioned 2, 3, and 4 m downwind from the nozzle. The wsp was scannedand DropletScan. software was used to measure percent area coverage for each treatment as a basis for separatingdifferences. For the crosswind orientation, the XR flat-fan measured significantly more downwind droplet coverage than theTT, DR, and AI flat-fans. The TT flat-fan had significantly less downwind droplet movement than the XR flat-fan at 47 L/ha,but not at 94 L/ha. The DR and AI flat-fans were not significantly different from each other, but did produce significantly lessdroplets moving downwind than both the XR and TT flat-fans. For the XR flat-fan, increasing the application volume from47 to 94 L/ha significantly reduced the amount of downwind droplet movement. This finding did not hold true for the TT, DR,and AI flat-fans. Similar trends were measured with the headwind nozzle orientation. As evidenced in this study, even whenused at the recommended pressure, the four nozzles compared produced significantly different amounts of downwind coverageon the wsp. Based on the findings, using nozzles specifically designed for reducing drift (TT, DR, and AI flat-fans) willsignificantly reduce drift when compared to conventional XR flat-fans.