Eliminating Spray Drift of Flat Fan Nozzle

Abstract

The objective of this research project is to eliminate the spray drift caused by crosswind. Spray drift is an important problem for the agricultural industry. Some herbicides (e.g. Dicamba) can cause serious damage if it drifts to nearby crops that are not genetically modified to withstand those herbicides. Our hypothesis is that the nozzle geometry and the injection angle can be actively/passively controlled to compensate for the crosswind. The present experimental setup consists of a commercial spray injection system with three different nozzles. The spray can be injected at different angles in the test section of a subsonic wind tunnel with a maximum air velocity of 60 m/s. The instrumentation consists of a pitot-static tube and an inclined manometer to measure the air velocity in the wind tunnel, a back-light illumination system, and a high-resolution camera. The spray images were analyzed using ImageJ software. The measurements include the breakup regime transitions, the droplet sizes, and the droplets trajectory as a function of the wind speed and the injection angle. The current results show that the crosswind modifies the primary breakup mechanism from sheet breakup regime (i.e. thinning and fragmentation of the liquid sheet into ligaments) to bag breakup regime (i.e. the formation bags along the downstream side of the liquid sheet) resulting in smaller drop sizes and an increased drift flux. Techniques to eliminate the bag breakup regime are presented.