STUDY ON DROPLET DEPOSITION IN PWM FLOW-CONTROLLED SPRAYING UNDER VARIABLE PRESSURE

The utilization rate of pesticides in China is low, which causes much pesticide waste and serious pollution of the ecological environment. The main reason of this problem is that the deposition rate of spray is not fairly high and the most fundamental factors affecting droplet deposition are the speed of droplet movement and the size of droplet particles. This study establishes a PWM intermittent spray system under variable pressure and flow control. Through CFD simulations, the atomization characteristics of the nozzle are analyzed. The results indicate that the system can generate finer droplet sizes and higher droplet velocities. By constructing a measurement platform for droplet experiments, tests are conducted on droplet sizes at different horizontal positions under four pressure levels: 0.3 MPa, 0.4 MPa, 0.5 MPa, and 0.6 MPa. The results indicate that as the spray pressure increases, the droplets exhibit a significant tendency to disperse toward both sides, and the droplet size decreases significantly. The field experiment is conducted with broad bean in flowering period. The results show that the average deposition rate increases by 9.9%, 26.4% and 22.9% when the spray pressure is 0.4 MPa, 0.5 MPa and 0.6 MPa compared with 0.3 MPa. This paper verifies the feasibility of the system in improving the spray pressure and quantitatively controlling the spray flow rate, and improving the deposition of droplets by obtaining finer particle size and higher spray velocity. In this sense, this paper has a certain reference significance for improving the effective utilization rate of pesticides and protecting the environment.