Analysis of Droplet Spectra and Spray Recovery as a Function of Atomizer Type and Fluid Physical Properties

Abstract

Drop size, as indicated by the volume median diameter (VMD), and size uniformity, noted by the relative span (RS), were correlated with (1) viscosity, (2) surface tension, (3) viscoelasticity, and also (4) liquid throughput. Two types of nozzles were used, simple orifices or jets and hollow cones. The density of the mixtures did not vary greatly and no correlations were made with this function. Increased liquid throughput (increased orifice diameter) showed significant effects on drop size, increasing the VMD as the orifice size increased for all nozzles and mixtures tested. Of the liquid properties, viscoelasticity had the greatest effect, increasing drop size as it was increased. Increasing the surface tension increased drop size significantly, but changes in viscosity appeared to have little effect on the drop size produced. The RS was reduced (narrow range) as surface tension, viscosity, and viscoelasticity were increased. Increased throughput reduced RS at two surface tension levels, but when the viscoelastic polymer was used, the increased throughput actually increased the RS for the nozzles tested. The atomization process is very complex and the study using kromkote paper collection cards could have benefited significantly if the new Particle Measuring Systems Co. (PMS) in situ system had been available. Nonetheless, the data have considerable relevance to pesticide spray atomization. Further advances will be made as the PMS or similar scanners become more widely available.

Spray deposition and drift during postemergence herbicide applications to turfgrass and annual flowers

“…Similar results were found by Yates et al (1976). Haq et al (1983) confirmed the basic relationship between liquid characteristics, nozzle type, and the effect of airstream shear by adding methanol to water to decrease the surface tension of the solution. They showed that increasing the surface tension of the solution from 20 dynes cm"' to 75 dynes cm"', increased the spray droplet vmd almost two-fold.…”

“…An increase in spray liquid viscosity results in the formation of larger droplets (Liljedahl, 1971). However, Haq et al (1983) found that increasing the spray solution viscosity by adding glycerol to water either had little effect on droplet size or increased the percentage of drops less than lOOjLtm in diameter. Akesson and Gibbs (1990) concluded that viscosity is effective in changing droplet size only when large changes occur from the addition of special additives such as spray thickeners, particulating agents, and foaming agents or when invert emulsions are used.…”

“…The Effect of Nozzle Size on Drift Haq et al (1983) concluded that the increased orifice diameter (flow rate) was the single most important factor affecting drop size. However, Adams et al, (1990) showed that the proportion of small droplets by number remained the same even though the volume of small drops decreased four-fold and the flow-rate increased six-fold by changing nozzles from a fine spray (XR 8001 VS") to a coarse spray (2080-30'^) .…”

Foliar Deposition and Off-Target Loss With Different Spray Techniques in Nursery Applications

“…Drift retardants were reported to reduce spray drift in many laboratory studies (Yates et al, 1976;Haq et al, 1982;Ozkan et al, 1992;Salyani and Cromwell, 1992;Smith, 1993). Laboratory tests indicated that drift retardants increased the volume median diameter of spray initially, but most polymer-based drift retardants lost effectiveness when recirculated through pumps (Bouse et al, 1988;Reichard et al, 1996;Zhu et al 1997).…”

Racionalización de las aplicaciones de productos fitosanitarios para el control de Aonidiella aurantii Maskell (Hemiptera: Diaspididae) en cítiricos.

“…Existen numerosos estudios sobre la influencia de las propiedades físicoquímicas del caldo en las distintas fases de la pulverización, principalmente sobre el espectro de los tamaños de las gotas pulverizadas y sobre la distribución de la deposición sobre el objetivo (Haq et al, 1983;Yates et al, 1983;Bouse et al, 1986Bouse et al, , 1988Bouse et al, y 1990Salyani, 1988;Wirth et al, 1991;Stevens, 1993;Schick, 1997Schick, y 2006Zhu et al, 1997;Hall et al, 1993;Butler-Ellis et al, 1997;Butler-Ellis y Tuck, 1999;Miller y Butler-Ellis, 2000;Jørgensen, 2000;Butler-Ellis et al, 2001;Holloway et al, 2000;Hewitt, 2001;Stainier et al, 2006;Zabkiewicz, 2007). Las características que más influyen sobre ambos aspectos son la tensión superficial, principalmente la dinámica, y, en menor medida, la viscosidad del caldo.…”