Development of a Variable Flow Rate Fan Spray Nozzle for Precision Chemical Application

Abstract

A new-concept variable-flow fan nozzle (VFFN) was developed for on-the-go variable rate application of crop production chemicals. A split-end meter plunger was variably positioned in a tapered sleeve to vary flow rate and create a fan spray. Ratio of maximum to minimum flow rate, or turndown ratio, was 13.3 to 1 for the prototype nozzle. Plunger actuation was accomplished with a pressure balance across a diaphragm. Control pressure on the top of the diaphragm balanced a supply line pressure on the bottom side. Three VFFN prototypes with spray angles of 50, 70 and 90 degrees were constructed and tested. By adjusting the control pressure from 414 to 138 kPa, the droplet spectrum D0.1 , Dv0.5 , and Dv0.9 were controlled from 58 to 190 mm, 141 to 522 mm, and 300 to 850 mm, respectively. Independent control of liquid flow rate and drop size spectrum was achieved by separately varying line pressure and control pressure. The spray angle of a VFFN, at a liquid line pressure of 276 kPa and a flow rate of 1.514 L/min, equaled the taper angle of the nozzle sleeve. For the taper angle of 90 degrees, the spray angle decreased from 90 to 65 degrees as flow rate was decreased from 1.514 to 0.227 L/min, and increased from 90 to 100 degrees as flow rate was increased from 1.514 to 3.028 L/min. A uniform spray distribution from the VFFN was monitored. The pattern width decreased by 36 percent as the flow rate decreased from 3.028 to 0.227 L/min.