The effect of fan setting, air-conveyor orientation and nozzle configuration on airblast sprayer efficiency: Insights relevant to trellised vineyards

A step-by-step laboratory procedure was used to identify the optimal configuration of a tower-shaped trailed sprayer intended for application in vertical shoot trellised vineyards. Different fan settings, air-conveyor orientation, and nozzle configuration were tested for their effect on both airflow pattern and vertical spray distribution. The optimal airflow rate at the fan outlet and the airflow velocity pattern at crop target distance were identified for different fan settings obtained by the combination of two fan gear speeds and three Power Take Off speeds (450, 500 and 540 rev min-1). The difference in the airflow pattern between factory air deflector settings and the adjusted ones was tested. Once the optimal fan setting was selected, the use of 12 or 16 active nozzles and 4 nozzle types was also tested. The optimal vertical spray profiles were determined based on defined thresholds of i) coefficient of variation, ii) amount of spray liquid lost above the target height and iii) two symmetry indices. The low fan gear speed combined with PTO set at 450 rev min(-1) result in the best option to reduce and obtain adequate air velocities. The adjustment of deflectors allowed to exactly match the spray to the canopy target height. Concurrently, the use of 12 nozzles drastically reduced the spray losses above the target height. Finally, 4 configurations out of 18, featured by the combination of a different nozzle type and number of active nozzles, met all the criteria set for optimal vertical spray profile.