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Pneumatic Control of a Variable Orifice Nozzle

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009618.(doi:10.13031/2013.36204)
Authors:   Joe D Luck, Michael P Sama, Santosh K Pitla, Scott A Shearer
Keywords:   precision agriculture, pesticide application, variable-rate technology, precision spraying, spray nozzles

A variable-orifice nozzle with droplet optimization was recently developed and introduced for use on agricultural sprayers. The VariTarget (VT) nozzle reacts to changes in the system flow rate via a metering assembly that is controlled by a diaphragm and spring. As the liquid pressure changes, the VT metering assembly attempts to control the flow rate and spray pattern exiting the nozzle. The goal of this study was to replace the spring controlled reactive system with a pneumatically controlled metering assembly. The proposed system would allow for the metering assembly to adjust the flow rate and spray pattern exiting the nozzle by increasing or decreasing air pressure on the diaphragm. Controlled with an electronic regulating valve, the diaphragm air pressure was tested to determine if desired flow rate variation could be achieved. Initial results indicated that increasing air pressure on the diaphragm results in a decreased flow rate through the nozzle as the input carrier pressure remained constant. The VT nozzle discharge rates for the four set carrier pressures (10, 20, 30, and 40 psi) ranged from as low as 0.2 gpm (maximum air pressure at 10 psi carrier pressure) up to 1.8 gpm (minimum air pressure at 40 psi carrier pressure). Based on these data the proposed pneumatic control system has the potential to provide a new method for variable-rate pesticide application where nozzle flow rates and spray patterns can be controlled pneumatically using sprayer system operating values and electronic regulating valves.

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