Spray Characteristics and Drift Reduction Potential with Air Induction and Conventional Flan Fan Nozzles

Authors: GULER, H - OSU; Zhu, Heping; OZKAN, H - OSU; Derksen, Richard; YU, Y - OSU; Krause, Charles

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2007
Publication Date: 4/8/2007
Citation: Guler, H., Zhu, H., Ozkan, H.E., Derksen, R.C., Yu, Y., Krause, C.R. 2007. Spray Characteristics and Drift Reduction Potential with Air Induction and Conventional Flan Fan Nozzles. Transactions of the ASABE. 50(3):745-754.

Interpretive Summary: Preventing drift from pesticide sprays has been and will continuously be a concern for pesticide applicators. The spray drift of pesticides in the air from the intended targets not only causes inefficient use of pesticides, but also causes damage on crops in adjacent fields, and potentially contaminates air, soil and water. During the past ten years, air induction nozzles (also called low drift nozzles) were recommended by some nozzle manufacturers and researchers to reduce spray drift because these nozzles can produce larger droplets and less portion of drift prone droplets than conventional hydraulic nozzles. However, air induction nozzles have not been studied thoroughly from engineering aspects for drift reduction. In previous studies, researchers selected nozzles with the same nominal flow rate to compare drift reduction potentials between air induction nozzles and conventional nozzles. No previous studies conducted investigation on comparing the drift reduction potentials between air induction nozzles and conventional nozzles with the equivalent orifice size under the same flow rate condition. Air induction nozzles are recommended using much higher pressure than conventional nozzles to obtain desired spray pattern width. Also, compared to conventional hydraulic nozzles, applicators have to pay higher price to purchase air induction nozzles. Thus, it is unclear to spray applicators whether air induction nozzles are designed following logical engineering principles theoretically and economically to produce droplets with low drift potential. In this study, laboratory experiments were conducted to compare spray drift reduction potential and other spray characteristics between air induction nozzles and conventional hydraulic nozzles with the equal orifice size operating at reduced operating pressures. Test results reported that the spray characteristics and drift reduction potential from air induction nozzles were actually similar to the conventional nozzles with equivalent orifice sizes operated at pressures close or below the manufacturer’s recommended pressure range. Therefore, pesticide spray applicators could use inexpensive conventional nozzles with low energy consumption to achieve the similar spray performances as the air induction nozzles.

Technical Abstract: Spray drift potential, spray coverage, droplet size, and spray pattern width for various sizes of air induction and conventional flat fan nozzles with equivalent orifice areas were investigated and compared under the laboratory conditions. Droplet sizes were measured with a laser imaging system, spray coverage on water sensitive papers (WSP) was evaluated with a boom sprayer at a constant travel speed in a greenhouse, and ground and airborne spray deposits were determined in a wind tunnel at two wind velocities (2.5 and 5 m/s). Tests were also conducted to evaluate the effect of air intake holes being closed or open on spray characteristics of air induction nozzles. With the equivalent nominal flow rate, air induction nozzles had approximately 2.1 to 2.75 times larger exit orifice areas than the conventional nozzles. With the equivalent orifice area and equal liquid flow rate, there was no significant difference in droplet size, spray pattern width, spray coverage, ground spray deposit, and airborne deposit among regular air induction nozzles, the air induction nozzles with two sealed air holes, and conventional flat fan nozzles. Spray characteristics of air induction nozzles could be achieved by conventional nozzles with the equivalent orifice size operated at the pressure below the manufacturer's recommended pressure range.