Submitted to: Journal of Plant Protection Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2013
Publication Date: April 16, 2014
Citation: Henry, R., Kruger, G., Fritz, B.K., Hoffmann, W.C., Bagley, B., Czazyck, Z. 2014. Measuring the effect of spray plume angle on the accuracy of droplet size data. In: Sesa, C., editor. Pesticide Formulation and Delivery Systems: 33rd Volume, "Sustainability: Contributions from Formulation Technology." West Conshohocken, PA: ASTM International. p. 129-138. DOI: 10.1520/STP1569-EB. Interpretive Summary: With an increased emphasis on managing off-target movement of sprays in agricultural applications, it is essential to understand the spray droplet distribution from spray nozzles for different spray pressures and solutions. Wind tunnel studies were conducted to assess the influence of spray plume orientation, which is the angle that the spray comes out of the nozzle, on measured droplet size spectra. These results showed that spray plume orientation does not affect droplet size data, regardless of spray pressure or solution. This work helped to establish standard laboratory practices and methods involving droplet size analyzers in low-speed wind tunnels; the work also enhanced validity of spray droplet data of value to the application industry, agrochemical manufacturers, and the U.S. EPA.
Technical Abstract: Analysis of droplet size data using laser diffraction allows for quick and easy assessment of droplet size for agricultural spray nozzles and pesticides; however, operation and setup of the instrument and test system can potentially influence the accuracy of the data. One of the factors is the orientation of the spray plume relative to the laser beam. The common practice is to orientate the nozzle such that the nozzle orifice’s long axis is 90 degrees from the laser beam. Some wind tunnels are designed in a manner such that the spray plume impinges with the walls or the design of the nozzle may necessitate a deviation from this standard practice to obtain a measurement in some situations. The objective of this research was to determine the influence spray plume orientation had on measured droplet size spectra in a low-speed wind tunnel. The orientation of the nozzle tested was 45, 60, 75 and 90 degrees in rotation relative to the laser beam. Four nozzles were evaluated using three different spray solutions. Treatments were evaluated using a laser diffraction system. The results indicate that spray plume orientation does not have an effect on droplet size data for these nozzles, regardless of spray solution. The data from these tests will aid in the standardization of laser diffraction use in low-speed wind tunnels and increase the repeatability of measurements between different spray testing laboratories.