Research On The Performance Of The Atomization Nozzle Of Plant Protection UAV Based On SLM Technology

With the improvement of China’s requirements for the development of precision agriculture,agricultural aviation has developed rapidly.As a pesticide application equipment for agricultural aviation,plant protection drones have the characteristics of high flexibility and wide terrain application,and can achieve the effect of pesticide application that cannot be satisfied by ground plant protection machinery.As one of the core components of plant protection drones,atomizing nozzles play an important role in the application of pesticides.At present,China’s plant protection drone nozzle technology is relatively backward,the production accuracy of the atomizing nozzle is low,it is easy to be damaged under the impact of the impact force,and the atomization performance of the plant protection drone atomizing nozzle is poor,resulting in pesticide waste and the environment pollution.Therefore,it is of great significance to study the fan-shaped atomizing nozzles of plant protection UAVs to improve the deposition and distribution uniformity of droplets,reduce the drift of droplets,and protect the environment.In this paper,the atomization performance of fan-shaped atomizer under different inlet pressures and outlet diameters is analyzed by numerical simulation,and the optimized nozzle is prepared by SLM technology,and the results are obtained by experiment and compared with numerical simulation.The main contents of the thesis are:(1)Based on the primary atomization of the multi-phase flow VOF model,the DPM model based on the Lagrange method is used to perform secondary atomization of the droplets.First complete the pre-processing process,extract the watershed in Geometry and establish the external atomizing field of the atomizing nozzle,and then import the CFD model into Mesh to define the boundary and mesh.The fluent multiphase flow VOF model is used to simulate the first atomization process of the nozzle at different inlet pressures.On the basis of the first atomization,the first atomized droplets are used in the DPM model based on the Lagrange method,Instability crushing model is used for secondary atomization simulation,and the relevant results of the droplet size of the external atomization field are obtained.(2)Determine the optimal inlet pressure of the nozzle,and then study the effect of the fan-shaped atomizing nozzle on the atomizing performance at different outlet diameters.First,the spray characteristics at different inlet pressures are studied to determine the optimal inlet pressure.Under the optimal inlet pressure,by changing the diameter of the outlet,its velocity field and droplet size are analyzed and studied.The atomization performance of the fan-shaped atomizing nozzle under different inlet pressures and outlet diameters is analyzed.(3)Based on SLM technology,a fan-shaped atomizing nozzle was prepared on the basis of optimizing the process parameters.Firstly,the process parameters for preparing the nozzle were studied.The laser power,scanning speed,scanning interval,and thickness of the powder layer were used as parameters,and the density,surface roughness,and tensile strength were used as optimization indicators.Based on the comprehensive equilibrium analysis method,the optimal process combination of SLM technology was determined.Based on this,a fan-shaped atomizing nozzle was prepared.(4)The prepared nozzles were tested experimentally,and the results were compared with the results of numerical simulation analysis,mainly including the changes of atomization angle,droplet velocity,droplet size distribution under the change of inlet pressures and outlet diameters.It can be seen from the experimental results that the experimental measurement results are basically consistent with the numerical simulation results,changing the inlet pressures and the outlet diameters have a great influence on the atomization performance.As the inlet pressure increases,the atomization performance is better,when the inlet pressure is the same,the increase in the outlet diameter also improves the atomization performance,but as the outlet diameter further increases,the atomization performance decreases instead.