A REVERSE VENTURI ATOMIZATION CHAMBER
Contact: Russ Stocker
Bob's Flying Service
3412 Laguna Avenue
Davis, CA 95616
Summary: Spray drift is one of the most significant issues facing aerial applicators. Material not applied to the target is a financial loss for the farmer and a potential liability for the applicator. Off-site drift also represents an environmental liability, particularly as habitat, water quality and urban encroachment concerns demand greater attention to larger buffer and/or no-spray zones. During conventional aerial applications, fluid leaving the nozzle is subjected to air shear resulting in an atomization profile (bell curve) with a portion of very small droplets (driftable fines). Increased airspeeds produce more driftable fines, increasing the potential for undesired off-site movement. Controlling the environment where atomization occurs reduces driftable fine production thereby reducing the potential undesired off-site movement of spray material. Control of the nozzle environment is accomplished using the Reverse Venturi Atomization Chamber (RVA). The RVA has three sections. Air enters the first section (diffuser), with a restricted opening, and flows into a larger area (settling chamber) where air velocities are reduced, the nozzle is located, and where atomization occurs. The atomized spray and air then travel together through the third chamber (constrictor) where they are accelerated to match the aircraft’s air speed. By reducing the air speed where atomization occurs, the atomization profile demonstrated by the RVA system produces fewer fines, resulting in less drift. The RVA chamber has demonstrated up to a 93% reduction in fines at 100 mph and 78% reduction in fines at 150 mph airspeed in wind tunnel testing. Actual drift testing with the RVA system on the testing aircraft at 150 mph in the field demonstrated a 40 percent reduction in drift at 50 meters downwind compared to a conventional spray system.