Location: Aerial Application Technology ResearchTitle: Update to the USDA-ARS fixed-wing spray nozzle models
|Fritz, Bradley - Brad|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2014
Publication Date: 4/15/2015
Citation: Fritz, B.K., Hoffmann, W.C. 2015. Update to the USDA-ARS fixed-wing spray nozzle models. Transactions of the ASABE. 58(2):281-295.
Interpretive Summary: Successful aerial applications start with proper spray nozzle selection and setup to insure droplet size meets both label requirements and meteorological and geographical conditions at the site of application. Since the development of the current USDA ARS aerial spray nozzle models, advances in measurement techniques, agricultural aircraft and spray nozzle technologies have necessitated updates to reflect current state of the art measurement techniques, new nozzles, and increased operational airspeeds and spray pressures. Data was collected for 12 aerial spray nozzles following specialized experimental designs that allowed for the development of mathematical models that predict droplet size characteristics at any combination of nozzle and aircraft operational settings. The new models greatly enhance the range of usability for the aerial nozzles tested and will be used to update computer and mobile device based user-interfaces providing aerial applicators with increased support in nozzle selection and setup to help meet agrochemical product labels and optimize applications.
Technical Abstract: The current USDA ARS Aerial Spray Nozzle Models were updated to reflect both new standardized measurement methods and systems, as well as, to increase operational spray pressure, aircraft airspeed and nozzle orientation angle limits. The new models were developed using both Central Composite Design and Custom Design Response Surface Methodologies which provide excellent fits to independently measured data (R2 values ranging from 0.81-0.99) for all droplet size parameters. The new models also updated droplet size classification ratings by adopting a previously recommended set of nozzles and operational pressures that provide similar data to ASABE Standard Reference nozzles, but are evaluated under aerial application conditions (primarily airspeed). Generally, for flat fan and deflection type nozzles, the new models result in increases to predicted DV0.1 data (droplet diameter at which 10% of the total spray volume is contained in droplets of equal or lesser diameter), decreases in DV0.5 and DV0.9 data (similar to DV0.1, but 50% and 90% total volume of spray) and increases in the percent of spray contained in droplets 200 µm or less. With straight stream nozzles, the DV0.1, DV0.5, and DV0.9 trends tend to be reversed. Droplet size classifications with the new models for flat fans and deflector type nozzles tend to shift ratings downward, as compared to the current models with classes centered around Fine and Medium Sprays. However with straight stream nozzles, droplet size classifications tend to shift upward as compared to that seen in the current models. The updated models will be used to populate spreadsheet and mobile device software based user interfaces to provide aerial applicators with droplet size information for an increased range of nozzles and operational settings allowing for better nozzle selection and operational guidance.