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Title: Spray adjuvant effects on droplet size spectra measured by three laser-based systems

Author
item Hoffmann, Wesley
item HEWITT, ANDREW - UNIV. OF QUEENSLAND
item ROSS, J - NEW MEXICO STATE
item BAGLEY, WILLIAM - WILBUR-ELLIS CO
item Martin, Daniel - Dan
item Fritz, Bradley - Brad

Submitted to: American Society for Testing and Materials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2008
Publication Date: 5/10/2008
Citation: Hoffmann, W.C., Hewitt, A.J., Ross, J.B., Bagley, W.E., Martin, D.E., Fritz, B.K. 2008. Spray adjuvant effects on droplet size spectra measured by three laser-based systems. Journal of ASTM International. 5(6):Paper ID JAI101233.

Interpretive Summary: Spray droplet size is a critical factor that impacts the efficacy, deposition, and possible drift of aerially applied crop protection products. Accordingly, accurate measurement of spray droplet size is important. Studies were conducted using three different droplet size measurement systems (Malvern, LaVision, and PMS) to determine the influence of eight spray adjuvants on the droplet size distribution produced by two nozzles in a high-speed wind tunnel. There were significant differences in the droplet size distribution produced by the eight spray adjuvants tested and between the droplet size values reported by the three measurement systems. These tests are the first reported studies where all three droplet size measurement systems were operated simultaneously. The results of this research will help researchers and applicators gain a better understanding of droplet size measurement systems.

Technical Abstract: Spray droplet size has long been recognized as the most important variable that aerial applicators can influence to mitigate spray drift from the application site. There are several different technologies that are used by researchers to measure droplet size from spray nozzles. The objective of these studies was to determine the influence of eight spray adjuvants on the droplet size spectrum produced by two nozzles in a high-speed wind tunnel when characterized using three different droplet size measurement systems. The adjuvant, nozzles and airspeeds are commonly used by aerial applicators. Three droplet sizing systems (Malvern laser diffraction, PMS optical array probe and LaVision laser imaging) were simultaneously operated for measurement of the spray from each adjuvant, airspeed, and nozzle combination. Two spray nozzles (a D6-46 nozzle and a D2 straight stream nozzle) were evaluated in a high speed wind tunnel at airspeeds of 45 and 58 m/sec. There were significant differences in the droplet size spectra produced by the eight spray adjuvants tested. There were also significant differences between the droplet size values reported by the three measurement systems (Malvern, LaVision, and PMS) evaluated; however, there was considerable agreement trend wise. In general, the Malvern reported smaller spray droplet size spectra values than the LaVision, while the PMS system generally reported the largest spray droplet size spectra values. These tests are the first reported studies where all three droplet sizing systems were operated simultaneously.