A Model to Predict Chargeability of Aerial Electrostatic Spray Nozzles for Fixed-Wing Agricultural Aircraft

Highlights Efficacy of electrostatically charged spray applications depends upon charge-to-mass ratio. Chargeability for electrostatic nozzles, TXVS-2, and TXVK-3, 4, 6 increased as airspeed increased. Droplet size increased with nozzle orifice size and decreased with airspeed and spray pressure. Chargeability was lower for nozzles with higher flowrate. An Excel-based model provides droplet size and charge-to-mass ratio data for aerial applicators. ABSTRACT. Optimizing electrostatically charged aerial sprays of pest control products on field crops by fixed-wing aircraft is required to incur beneficial advantages such as improved deposits, increased plant canopy penetration, and a wrap-around effect associated with this technology. A spray mixture of tap water and a non-ionic surfactant was atomized through four electrostatic nozzles, TXVS-2, TXVK-3, 4, and 6, at seven sets of airspeed and nozzle spray pressure combinations in a high-speed wind tunnel to determine spray chargeability. Using the parameter estimates (airspeed, nozzle orifice, liquid spray pressure, spray droplet spectra, and flowrate), a response surface model was developed and incorporated into a Microsoft Excel-based app, which can be installed and run on a smartphone. The goodness-of-fit of the model showed that the R 2 values for the spray droplet spectra used to build the model ranged from 0.941 to 0.985, which indicates that the measured values closely approximated the modeled values. This model can help aerial applicators maximize the chargeability of electrostatically charged aerial sprays and conform with label requirements specified for the application of crop protection chemicals. This may help improve efficacy and mitigate off-target movement of crop protection products. Keywords: Airspeed, Charge-to-mass ratio, Electrostatic nozzles, Liquid spray pressure, Modeling, Spray charge, Spray droplet spectra.