ATOMIZATION OF AERIAL SPRAY NOZZLES AT AIRSPEEDS ABOVE 160 MPH

by

Brad Fritz, Clint Hoffmann

Contact: Bradley K. Fritz

Agricultural Engineer

Aerial Application Technology Group

USDA ARS

2771 F&B Road

College Station, TX 77845

brad.fritz@ars.usda.gov

(979) 260-9584

Summary: Most aerial applicators are familiar with the Spray Nozzle Models developed by the USDA ARS Aerial Application Research (AAT) group. These models are available for a number of commonly used aerial spray nozzles and allow users to estimate the spray droplet size based on the nozzle setup, orientation, spray pressure and airspeed. Presently these models are only valid for spray pressures up to 60 psi and airspeeds up to 160 mph, but with the continued performance improvements and developments in modern agricultural aircraft, there is a need to investigate the effects that airspeeds beyond the 160 mph limit have on spray atomization. This manuscript will detail the features of a new high speed wind tunnel system at the AAT facilities that is capable of generating airspeeds up to 220 mph, as well as, a scrubber system that will allow for future atomization studies to be conducted with active ingredients. The atomization characteristics of several aerial spray nozzles at airspeeds exceeding 160 mph are measured and reported. Determining how these nozzles perform at higher airspeeds will help to improve present nozzles and/or develop new nozzles or application techniques, to counter the increased atomization seen at these higher airspeeds. Additionally, these new facilities will allow for expanding the Spray Nozzle Models to provide applicators guidance on spray nozzle selection and setup at airspeeds beyond 160 mph.

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