Spray Droplet Size for Water and Paraffinic Oil Applied at Ultralow Volume

Abstract

Spray droplet size of water and paraffinic oil was affected by air pressure, nozzle type, and liquid flow rate when applied with an ultralow volume (ULV), air-assist sprayer. Volume median diameters of water were generally larger than oil at constant air pressure and liquid flow rate. Droplet size decreased as air pressure increased, but increased as liquid flow rate increased. Volume median diameters of water droplets ranged from 41 to 838μm and from 16 to 457μm with oil when atomized at air pressures ranging from 14 to 84 kPa. Relative spans ranged from 1.2 to 18.0 and 2.0 to 7.2 for water and oil, respectively.

Effect of Drift Retardant Adjuvants on Spray Droplet Size of Water and Paraffinic Oil Applied at Ultralow Volume

“…Droplet size distributions were determined with a laser particle analyzer 4 * mounted in an enclosed spray chamber to minimize air movement around the spray as measure ments were made. An air-assist spray system (7,8,12) with a Bete T-Mizer 5 nozzle was used to atomize all solutions for evaluation of spray droplet spectra. The nozzle was mounted 235 mm above the laser beam on a three-dimen sional positioner (8) which allowed precise positioning of the nozzle and traversing the entire spray pattern through the laser beam of the particle size analyzer at a constant speed.…”

“…Air was supplied from a large-capacity compressed-air system, regulated near the nozzle with pressure measured at the nozzle with a liquid-filled gauge. Liquid flow rate calibrations were conducted by measuring fluid removed from a graduated cylinder on the suction side of the pump as described by Hanks and McWhorter (7,8).…”

“…Paraffinic oil 8 was evaluated without adjuvant and with EX100 9 and PR945E® 10 at concentrations of 0.125, 0.25, and 0.5% (w/w) and (v/v), respectively. Liquid flow rates and air pressures were the same as with water, except atomization of oil sprays at 14 kPa was not adequate in most circumstances, therefore data were omitted.…”

“…Herbicides have traditionally been mixed with water and sprayed with a conventional hydraulic system at spray volumes of 94 to 187 L/ha. Considerable research has been conducted to evaluate diluents other than water as a carrier (8,11,12,13,14,16) and reduced spray volumes (2, 6, 7, WEED TECHNOLOGY 8,11,12,13,14,16). Changes in spray volume and/or diluent have resulted in better efficacy, often at significant reductions in herbicide rates.…”

Effect of Oil Adjuvants and Nitrogen Fertilizer on the Efficacy of Imazethapyr Applied at Conventional and Ultralow Spray Volumes

“…The spray pattern and droplet size are formed by a low-pressure airflow that is introduced at the nozzle tip (Hanks and McWhorter 1993). The flow rate from the positive displacement pump was found to vary less than ± 1 % when water and oil were mixed at different ratios and the pump capacity was varied from 1 to 100% (Hanks and McWhorter 1991).…”