Effects of nozzle types, adjuvants and environmental conditions on spray drift potential of unmanned aerial vehicles in a wind tunnel

In order to investigate and reduce spray drift during the use of plant protection unmanned aerial vehicles (UAV), a spray unit consisting of a single rotor and a nozzle was simulated under the controlled wind tunnel conditions (wind speed 5 m/s, spray pressure 0.3 MPa and rotor speed 2 300 r/min). The effects of 11 kinds of nozzles and 4 different adjuvants on droplet drift were investigated. The drift potential index (DIX) and drift potential reduction percentage (DPRP) were also evaluated and compared. The results show that under the condition of 20℃/RH 80%, the drift distribution of different nozzle types in vertical plane and horizontal distance showed a regular change trend. Compared with the reference nozzle F110-03, the order of the drift potential of nozzles from large to small was TR80-0067 > ST110-0067 > XR110-01 > ST110-015 > TR80-01 > ST110-02 > XR110-03 > F110-03 > IDK series. The effect of IDK120-01and IDK120-015 was similar and they were the best ones. Under the wind tunnel condition of 30℃/RH 40% and wind speed of 5 m/s, compared to the control group without adjuvants, the mean drift reduction rates of spray nozzle XR 110-01 with adjuvant of 0.5% Silwet DRS-60, 1.0% "Maifei" (MF) and 1.0% Y-20079 were 43.3%, 15.6% and 5.2%, respectively. The selection of drift reducing adjuvants needs to consider the type of adjuvants and their effects. At the wind tunnel conditions of 20℃/RH 40%, 20℃/RH 80%, 30℃/RH 40% and 30℃/RH 60%, the spray nozzle XR110-01 added with 1.0% MF adjuvant was beneficial to the reduction of airborn drift. Especially, under high temperature and low humidity conditions, it had better drift reduction effect. This study has provided reference and guidance for nozzles selection, adjuvants selection and the field application of UAV for plant protection, and also data basis for the further study of the drift reduction technology of nozzle and adjuvants.