The RHEA airblast sprayer: studies on intermittent flow rate nozzle for the VRA.

Current commercially technologies for the pesticides management are designed in many configurations, allowing a wide range of regulation, which however must be accompanied by technical and operational skills of the user. This condition introduces variable risks in relation to the proper configuration of the spray machine and the correct operating set-up and procedure. These aspects may be solved today by the introduction of sensor systems and operational monitoring tools to assist the operator work. In the project RHEA (robot fleets for highly effective agriculture and forestry management), the Florence O. U. has the aim to develop a sprayer prototype for the tree crops treatments to manage in real time, the quality and quantity of the pesticide mixture distributed and the intensity and direction of the air, depending on the structural variability of the canopy. For the variable rate application of dose in accordance with the canopy thickness it has been developed and tested the concept of pulsating flow rate technique that controls each nozzle in an independent way. To obtain an intermittence flow rate is applied, on the nozzles, an high frequency solenoid valve (HSFV) with the purpose of interrupting the pesticide flow rate. This is adjusted by acting on two parameters of the HSFV: frequency and duty cycle. The obtained data were processed and evaluated to verify the spray cloud features varying frequency and duty cycle adopted. Variation in terms of flow rate and of the droplets diameter were analyzed. In this preliminary study, significant results were obtained by adopting frequency of 8Hz and 10Hz with reductions of the flow rate respectively of 44%, with 30% duty cycle and 25%, with 50% duty cycle, obtaining the same amount of the flow reduction independently of the type nozzle used.