Modeling the Droplet Size Distribution of Atomizers with Different Cage Diameters for Large-Payload Unmanned Aerial Vehicles (UAVs)

Spraying drift is a key concern in aerial spraying and relates closely to droplet size. With the growing application of large-load UAVs, large-load plant protection UAVs lack corresponding spraying devices. The rotary cage atomizer, suitable for high-flow aerial spraying, is a better option for large-load plant protection UAVs’ spraying needs. A modified rotating cage atomizer based on the AU5000 atomizer in manned aircraft was designed, with cage diameters of 76 mm, 86 mm, 96 mm, 106 mm, and 116 mm. Based on the IEA-I high-speed wind tunnel, this study investigated the impacts of different wind speeds, flow rates, and cage diameters on the atomization characteristic distribution of the modified atomizer and established a model. The results show that when other variables remain constant, for every 1 mm increase in cage diameter, the average droplet size decreases by 0.944 μm. The R2 of the predicted values and the measured values of the droplet size model is 0.917. Under the conditions of 50 m/s, 58.3 m/s, and 66.6 m/s wind speeds, as the cage diameter increases, Relative Span (RS) shows a trend of first increasing and then decreasing. Among them, the RS of the 106 mm cage diameter is usually the highest. This study can provide a reference for the aerial spraying scheme of large-payload plant protection UAVs, such as the selection of the diameter of the rotating cage.