CHARACTERIZATION OF HYDRAULIC NOZZLES FOR DROPLET SIZE AND SPRAY COVERAGE

Abstract

Spray coverage specifications for commercially available nozzles could help applicators determine the optimal nozzles for effective control of insects, diseases, and weeds. Spray coverage and deposit density from seven types of nozzles at three different flow rates (0.76, 1.14, and 2.27 L min−1) and two target positions (0.50 and 0.70 m below the nozzle) were evaluated with water-sensitive papers (WSP) as targets under controlled environmental conditions. These nozzles included 80°and 110° conventional flat-fan nozzles, air induction flat-fan nozzles with the air intake hole either opened or sealed, hollow-cone nozzles, turbo jet nozzles, and twin-jet fan pattern nozzles. Spray coverage (percent area of a WSP covered with spray depositions) increased as flow rate increased for all nozzles. The hollow-cone nozzles had the highest coverage at both target positions while air induction nozzles had the lowest coverage.With the same flow rate, the 80° nozzles had higher spray coverage than 110° nozzles. Nozzles producing coarse spray had the lower spray coverage than nozzles producing fine and medium sprays. The 80° and 110° flat-fan nozzles at lower-than-specified operating pressures produced spray as coarse as that from the air induction nozzles with similar coverage. There was no significant difference in spray coverage between the same air induction nozzles whether the two air intake holes were opened or sealed. Spray coverage on targets at the 0.50 m position was greater than that at the 0.70 m position. Therefore, careful selection of nozzles could provide comparable performance for economical and effective spray coverage with optimal flow rates and operating pressures.