Design And Experimental Study Of Electrostatic Spray System Based On Multi Rotor UAV

Compared with traditional plant protection,UAV plant protection can break the terrain restrictions,increase efficiency and save energy.Electrostatic spray can make the spray droplet charged,accelerate the movement of droplets,and better droplet adsorption and penetration were obtained.Electrostatic spray can increase the residence time of droplets on the leaves of crops.On the other hand,droplets can effectively penetrate the back of the leaves and narrow space.The drifting phenomenon of UAV’s plant protection operation can be reduced by combining UAV and electrostatic spray,and the rotor wind field generated by UAV can also enhance the adsorption effect and penetration performance of droplets,thus improving the quality of plant protection.The paper designed an electrostatic spray system based on the multi rotor UAV platform.The droplet deposition characteristics and the UAV downwash airflow field are numerically simulated by using computational fluid dynamics(CFD)discrete term model and magnetohydrodynamics(MHD),and the electrostatic spray system mounted on a multi rotor UAV is experimentally studied.The specific research contents are as follows:(1)Theoretical analysis of electrostatic spray was carried out and numerical simulation and bench test were carried out.The simulation results show that the average droplet deposition rate of electrostatic spray is higher than that of conventional spray when the ambient wind speed is 0～3 m/s and the spray height is 30～200 cm.The maximum difference can reach 58%.The error between the bench test and the simulation result is less than 10%,which further verifies the reliability of the simulation model.(2)Numerical simulation and experimental study on the downwash airflow field of UAV are carried out.The simulation shows that the downwash airflow field is mainly concentrated below the UAV rotor,and the wind speed reaches the peak at 100 cm away from the rotor.The distribution trend of the airflow field is basically consistent with the test results.Through the coupling simulation of UAV downwash airflow field and electrostatic spray field,it is found that the lower pressure produced by the downwash airflow field can increase the spray deposition amount.Within the 1～5 m/s range of the ambient wind field,the electrostatic spray deposition of UAV is higher than that of UAV conventional spray and ground plant protection.Electrostatic field has certain wind resistance to the wind field.(3)Developed an airborne electrostatic spray system based on Dajiang MG-1P eight rotor plant protection UAV platform and the charge to mass ratio test was carried out.The system uses contact-charging to generate static electricity.The charge balance of UAV fuselage is carried out through bipolar single system.The contact electrostatic nozzle and electrostatic spray rod with expansion range of less than 40 cm are designed.The maximum charge-mass ratio of the system measured in the test is 1.18 m C/kg,which verifies the reliability of the system.(4)The performance test of electrostatic spray system for UAV is carried out.Single factor experiments were carried out on spray pressure,leaf density index and spray height which affected the quality of electrostatic spraying.The results showed that the average loss of electrostatic spray was smaller than that of conventional spray at the pressure of 0.4～1.0MPa,0.5～2.5 of leaf density and 50～130 cm of spraying height.The response surface analysis showed that the significant factors affecting the electrostatic spray penetration were:spray height > leaf density index > spray pressure.