DROPLET SIZE AND SPRAY PATTERN CHARACTERISTICS OF AN ELECTRONIC FLOW CONTROLLER FOR SPRAY NOZZLES

An electronic flow control system for pressure atomization spray nozzles was evaluated. The control actuator was a direct-acting, in-line solenoid valve directly coupled to a standard agricultural spray nozzle tip. Variable flow was obtained by varying the frequency and duty cycle of the valve operation. The ratio of maximum to minimum volumetric flow rate over the range of continuous control (i.e., the turndown ratio) was 3·21:1, 3·55:1 and 2·51:1 for flat-fan, hollow-cone and solid-cone nozzle tips, respectively. Actuator frequencies, duty cycles and the corresponding turndown ratios were physically limited by the time required for complete opening and closing of the valve. The effects of the flow controller on the droplet size spectra and spray distribution patterns of the nozzles were quantified. As the nozzle flow was reduced from the uncontrolled (maximum) rate to the minimum controllable rate, the observed volume median diameter of the spray droplets increased by 8·1, 23·1 and 29·7% for the flat-fan, hollow-cone and solid-cone tips, respectively. For all nozzles tested, reduction in flow rate resulted in a more narrow spray distribution pattern. © 1997 Elsevier Science Ltd. All rights reserved.