The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study was divided into a static test and a dynamic test. During the static test, the air velocity in the working vicinity of the sprayer was measured considering the following machine configurations: (1) one activated fan regulated at three air flows (machine working as a traditional sprayer); (2) two activated fans regulated at three air flows for each fan. In the static test 72 measurement points were considered. The location of the measurement points was as follow: left and right sides of the sprayer; three sections of measurement (A, B and C); three measurement distances from the shaft of the machine (1.5 m, 2.5 m and 3.5 m); and four measurement heights (1 m, 2 m, 3 m and 4 m). The static test results have shown significant differences in the module and the vertical angle of the air velocity vector in function of the regulations of the sprayer. In the dynamic test, the air velocity was measured at 2.5 m from the axis of the sprayer considering four measurement heights (1 m, 2 m, 3 m and 4 m). In this test, the sprayer regulations were: one or two activated fans; one air flow for each fan; forward speed of 2.8 km/h. The use of one fan (back) or two fans (back and front) produced significant differences on the duration of the presence of wind in the measurement point and on the direction of the air velocity vector. The module of the air velocity vector was not affected by the number of activated fans.

An acoustic Doppler velocimeter (ADV) was used to analyse the impact of an agricultural sprayer’s agitation system settings on fluid velocities inside the tank. A 3000 L capacity sprayer equipped with a 4-nozzle hydraulic agitation system was used. ADV measurements were carried at 32 points inside the tank under the following settings: circuit pressures of 8, 10, or 12 bar; water level in the tank of 1000, 2000, or 3000 L; 2 or 4 active nozzles. An agitation test with a concentration of 0.4% copper oxychloride was employed to analyse the concentration of active matter as a function of tank fill level and number of active nozzles. All parameters significantly affected the fluid velocity, which increased with increasing pressure, but decreased with increasing water level in the tank and an increased number of active nozzles. Concentration tests showed greater active matter concentrations when higher velocities were recorded by the ADV. The ADV was shown to be a useful tool for the rapid assessment of fluid velocities; in the future, it could be used to validate the design of agitation systems, and to estimate their capacity to ensure an adequate level of active matter concentration in the fluid.

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A computational fluid dynamics (CFD) model of the air flow generated by an air-assisted sprayer equipped with two axial fans was developed and validated by practical experiments in the laboratory. The CFD model was developed by considering the total air flow supplied by the sprayer fan to be the main parameter, rather than the outlet air velocity. The model was developed for three air flows corresponding to three fan blade settings and assuming that the sprayer is stationary. Actual measurements of the air velocity near the sprayer were taken using 3D sonic anemometers. The workspace sprayer was divided into three sections, and the air velocity was measured in each section on both sides of the machine at a horizontal distance of 1.5, 2.5, and 3.5 m from the machine, and at heights of 1, 2, 3, and 4 m above the ground The coefficient of determination (R2) between the simulated and measured values was 0.859, which demonstrates a good correlation between the simulated and measured data. Considering the overall data, the air velocity values produced by the CFD model were not significantly different from the measured values.