Spray drift is one of the most significant issues presently facing agricultural applicators throughout the United States. In American agriculture, up to half of the crop production materials applied are delivered to the crop by air. However, material that drifts off-site is of concern. Material not applied to the target crop or pest is a financial loss for the farmer and a potential liability for the applicator if damage occurs. Off-site drift also represents an environmental liability, particularly as habitat and water quality concerns demand more and larger buffer and/or no-spray zones. The proposed reverse venturi atomization (RVA) chamber is a potential strategy to mitigate the problem of off-site drift. Current practice delivers liquid material through a nozzle, under pressure, and utilizes air shear for at least a portion of the atomization. This atomization creates a range of droplets with those in the less than 200 micron range, known as fines, particularly susceptible to off-site drift. As the speed of application increases, so does the effect of air shear on the atomized droplets, resulting in larger droplets shattering or fracturing into fines. By creating spray droplets within the RVA chamber (which is a controlled environment than allows atomization to take place in a calmer environment), we propose to minimize the effect of air shear, reduce the overall percentage of droplets in the less than 200 micron range, and ultimately reduce the potential for material applied by air to drift off-site. OBJECTIVES: The objective of this phase I study is to optimize the Reverse Venturi Atomization Chamber design so it has the least aerodynamic effect on the aircraft while at the same time making the diffuser and constriction sections of the chamber most efficient. Obtain the atomizer (nozzle) with the optimum atomization profile having the leased number of fine droplets (less than 200 microns) and the least number of large droplets (larger than 1000 microns). Join the improved Reverse Venturi Atomization chamber and the optimal atomizer into a combined working system. Evaluate the aerodynamic effects and characteristics this system will have on aircraft. APPROACH: The work plan has four basic steps: Find a nozzle or group of nozzles with an optimal droplet spectrum (minimization of both fine droplets less than 200 microns and larger droplets greater than 1,000 micron) that can then be utilized as is or modified to operate successfully in the reverse venturi atomization chamber (RVA). There is the potential that modifications to existing nozzles and/or custom designed nozzles will be required to meet the objectives of this study. Nozzle evaluations will include: shape of spray pattern under static and airflow (0 to 150 mph) conditions, determination of an optimum atomization profile at air speeds from 50 to 150 mph and at different spray pressures for each nozzle in the wind tunnel using the PMS system to measure droplet spectra. Refine the configuration of the RVA chamber. The goal for this objective is to minimize the size while optimizing the performance within the chamber and the acceleration of the spray material (without creating fines) to ambient airspeed as it leaves the chamber. Currently we have three chamber designs. Newer designs will have less aerodynamic effects on the airplane while at the same time modifying the diffuser section eliminating the need for boundary layer ejection slot with a more rapid constriction section making a more efficient chamber. Chambers with new configurations will be tested in the wind tunnel using a survey rake and manometer board to establish air velocities inside of the chamber. After appropriate chamber design, two different chambers will be constructed, one to operate at 100 mph and the other at 150 mph. Test the most likely nozzles and chamber configuration(s) in the wind tunnel. Once the nozzle atomization spectra and profiles have been completed, likely nozzles identified, and the aerodynamic characteristics of the chambers have been optimized, these two components will be combined and tested as a system in the wind tunnel using the PMS system at both 100 mph and 150 mph with the corresponding chamber. Evaluate mounting and aerodynamic effects of the chamber on the aircraft. We will specifically evaluate the chamber for: drag, optimum mounting points, effects of pitching moment, the effect of stability, control and flight quality
