| Plant protection drone low-altitude low-volume spray technology has become more and more widely used in plant protection field with the advantages of high efficiency and safety.However,the distribution of the wind field of the drone is disorderly,and the deposition rules of the droplets of different particle sizes are different,which makes it difficult to further analyze the adhesion law of the droplets.Therefore,it is of great significance to study the wind field,droplet size and the adhesion of droplets on the surface of crop leaves.The specific research work and results are as follows:(1)Using CFD numerical simulation technology to simulate the downwind wind field of the eight-rotor plant protection drone,and setting four different rotor speeds to obtain the corresponding velocity contour and velocity vector.The wind field is mainly concentrated under the drone.The strength of the wind field below the rotor appears to increase at first and then weaken.The vortex phenomenon formed around the rotor and between the rotors.The increase of the rotational speed of the rotor causes the wind field coverage of the drone to be larger,at the same time,the wind field is more disordered and strong,and the vortex phenomenon is more obvious.(2)Aiming at the curl phenomenon of rice leaves after in vitro,a preservation method of in vitro rice leaves was proposed to prolong the observation life of isolated rice leaves.Attachment points of dye droplets on rice leaves were observed in the four time periods:after the leaves were in vitro,transporting,making the specimen,7 days later of specimen preparation was made.The results confirmed the feasibility of the method.(3)Through the experiment to explore the change of the droplet size,it can be concluded that the centrifugal disc rotation speed is the main reason for determining the particle size of the droplet.The rotation speed of the centrifugal disc is inversely proportional to the droplet size.As the height increases,the droplet size becomes smaller and the variation is getting lower.There is no significant effect of rotor speed on droplet size.(4)The critical diameter of droplet drop on rice leaves was deduced,and the droplets were deposited at the main deposition sites of rice leaves.It was concluded that the droplets were not easy to fall off in the burr area,the silicified wood belt area was second,and the other areas combined with foreign droplets were obviously lower than the first two.The ability is significantly lower than the first two.(5)Subsequent field experiments conducted a statistical analysis of the adhesion ratio of droplets to different micro-structures of rice leaves and the droplets in rice leaves.It is concluded that the ability of the burr area to combine foreign droplets is stronger than that of the silicified wood zone and other areas;the adhesion of proportion and domination about the droplet adhesion track diameter below 50 ?m;the droplet size is in accordance with the requirements of the low spray size;the uniformity of the droplet size consistent with the low spray size requirements is higher than the range.In the range of 150 to 250 microns,the uniformity of small droplets is higher than that of large droplets,which embodies the advantages of low-altitude and low-volume spray technology.The simulation of the drone wind farm provides a reference for the installation of the airborne spray device.The spray head should be installed directly below the rotor,and the spray height is lower than the frame legs.Investigate the factors affecting the variation of droplet size and spray deposition,determine the optimal spray parameters in accordance with the standard,and prove the advantages of low-altitude low-volume spray technology by uniformity of droplet distribution. |
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