Effects of formulation on spray nozzle performance for applications from ground-based boom sprayers

Abstract

The performance of agricultural spray nozzles has components relating to the droplet size and velocity distributions within the spray, spray structure, entrained air characteristics and the spray volume distribution pattern. The interaction of these physical performance parameters has been shown to influence target retention, efficacy and the risk of drift. Results from a number of studies have also shown that the physical properties of the spray liquid have a substantial effect on spray formation such that changes in formulation type can give changes in spray characteristics that would be equivalent to doubling the flow rate through conventional hydraulic flat fan nozzles. The interactions between the physical properties of the spray liquid and the characteristics of the spray formed is a function of nozzle design. However, analysis of a large data set for a range of types of hydraulic pressure nozzle has shown that sprays formed from liquids based on emulsions generally have a coarser droplet size distribution compared with sprays formed from surfactant solutions. Although some correlation between dynamic surface tension and viscosity with spray droplet size has been established, the results from work reviewed in this paper suggest that other factors also influence the spray formation process. Air induction and twin-fluid nozzles mix air and liquid in the spray formulation process to produce droplets with air inclusions. These nozzle designs have been found to have a performance that is more sensitive to changes in spray liquid properties compared with hydraulic pressure nozzles and to exhibit trends that are different from those of conventional nozzle types.