Submitted to: Transactions of the ASAE
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/29/2001
Publication Date: N/A
Citation: Interpretive Summary: Spray drift from pesticides applied to crops with boom sprayers is a major problem facing agriculture. Many studies have used mechanical shields to reduce the amount of spray moving out of the target field. This is the first study to try to model a curtain (jet) of air used to shield the spray nozzle from wind effects. In this study, we used a computational fluid dynamics program, FLUENT, to investigate the optimum design parameters for air jet shields. In addition, simulations were conducted of similar air jets, used on some commercial sprayers to aid spraying efficiency. Both air assisted and pseudo airshear spraying were simulated and compared with the best air shield design. Relative drift potential (shielded sprayer drift compared to unshielded sprayer drift) was calculated by following the trajectories of many droplets to determine their fate (deposit on ground, transported out of the model region by air currents, or evaporated). Not all air shield designs decreased relative drift potential. However, the optimum air shield design did reduce relative drift potential substantially. In these simulations, the best air shields decreased relative drift potential about the same as available commercial air assisted and pseudo air shear systems. This type of modeling can be used to quickly evaluate boom sprayer/air shield designs that produce a minimum of spray drift and deposit a maximum of spray on the target crop. This method has been used to design prototype sprayers in Taiwan and should have wide application in the rest of the world.
Technical Abstract: Shielding spray booms is one strategy recommended for reducing spray drift. Although many studies related to mechanical shields show positive effect on reducing spray drift, little information about the use of pneumatic shields is available. In this study, by means of a computational fluid dynamic software package, FLUENT, designs of several pneumatic-shielding designs were rated based on drift reduction. For relative comparisons, conventional spraying using nozzles, air-assisted spraying and air-shear spraying were also included in the analysis. Results of this study indicate that not all simulated cases of pneumatic shielded spraying provided better drift control. To ensure a better drift reduction and reduce the power required for pneumatic shielded spraying, the optimal operating parameters for the dominant variables appeared to be jet velocity of 40 m/s, jet flow rate of 1.7 m3/s/m and jet angle of 15 degreees forward. Optimal operating parameters, obtained from a multi-factor analysis of variance, were similar to results from previous studies on air-assisted and air-shear spraying. Pneumatic-shielded spraying, with proper choice of operating parameters, may be a suitable alternative to reduce spray drift.