Study On The Mechanism And Technology Of Selective Laser Melting Super Hydrophobic Agricultural Nozzle

Unmanned aerial vehicle(UAV)aerial spraying has developed rapidly in China in recent years due to high prevention and control efficiency,low environmental pollution,and low operating costs.Centrifugal atomizer is a kind of plant protection nozzle widely used in unmanned aerial vehicles.The operation efficiency is reduced because the liquid viscosity consumes a lot of energy.Therefore,it is great significance to research on drag reduction and energy conservation of the centrifugal atomizer.In this paper,an inverted trapezoidal structure with superhydrophobicity was designed,and a centrifugal atomizer with this structure was formed by using selective laser melting(SLM)technology.Comparative study of the contact angle of water droplets measured on the surface of untreated,storage in air for two weeks,heat treated and chemically modified parts was aimed at characterizing superhydrophobic properties and analyze the wettability transition mechanism;Corrosion resistance and corrosion resistance mechanism of the surface were analysed with electrochemical corrosion tests;Surface abrasion performance and the abrasion mechanism were studied with the friction and wear test.The droplet size,droplet deposition amount,and spray pattern performance of the superhydrophobic centrifugal atomizer were studied and analyzed to verify the low resistance characteristics of the superhydrophobic centrifugal atomizer.The main research contents and conclusions of the paper are as follows:(1)The structural parameters of the inverted trapezoid structure were optimized based on experiments to obtain the optimal structural parameters: the upper surface diameter is0.48 mm,the lower surface diameter is 0.2mm,and the overall height is 0.5mm.The distance between the two microstructures is 0.16 mm.The experimental results showed that the contact angle of the water droplets of the parts after storage in air for two weeks is 156 °,the contact angle of the water droplets of the parts after heat treatment is 155 °,and the contact angle of the water droplets of the parts after chemical modification is 160.2 °.The surface chemical composition of the parts affected the hydrophobicity of the parts.(2)Electrochemical corrosion research showed that: microstructure can improve corrosion resistance of the material,and chemically modified parts have strong corrosion resistance;wear tests showed that the microstructure can reduce friction coefficient of the material.The storage in air for two weeks,heat-treated treatment and chemically modified material lost superhydrophobicity after being worn by 500 g load for 7,20 and 40 minute respectively.The friction coefficient of the chemically modified material was the Minimum only 0.2228.The surface was covered with fluoride and produced a secondary structure after the wear test.The wear modes are mainly abrasive wear and oxidative wear.(3)The experiment on the particle size of the super-hydrophobic centrifugal atomizer shows that the particle size of the superhydrophobic centrifugal atomizer decreased as the rotation speed of the atomizing disk increased.It increased with the increase of the input flow.The atomization method were fogdrop fragmentation,jet fragmentation and the coexistence of the two methods.The minimum particle size of the droplet was 156 μm,which meets the requirements of biological control.The spraying range of the hydrophobic centrifugal atomizer is a circular area,and the droplet distribution in the spraying area was a certain normal distribution.When the rotation speed of the atomizing disk decreased,the droplets gradually gather to the middle,the droplet deposition uniformity became worse and the spray width decreases.When the input flow rate increased,the total number of droplets increased,and the distribution uniformity became worse,which has little effect on the spray width.Compared with the no superhydrophobic centrifugal atomizer,the superhydrophobic centrifugal atomizer consumed less power,has a certain low-resistance characteristic,and has the characteristics of refining the droplets.