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

The performance of agricultural spray nozzles has components relating to th e 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 f ormulation type can give changes in spray characteristics that would be equ ivalent to doubling the flow rate through conventional hydraulic flat fan n ozzles. The interactions between the physical properties of the spray liqui d and the characteristics of the spray formed is a function of nozzle desig n. 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 emulsion s generally have a coarser droplet size distribution compared with sprays f ormed 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 al so influence the spray formation process. Air induction and twin-fluid nozz les mix air and liquid in the spray formulation process to produce droplets with air inclusions. These nozzle designs have been found to have a perfor mance that is more sensitive to changes in spray liquid properties compared with hydraulic pressure nozzles and to exhibit trends that are different f rom those of conventional nozzle types. (C) 2000 Elsevier Science Ltd. All rights reserved.