| China is a big country in terms of citrus production.In China,the amount of citrus production and planting area rank first in the world.The area of citrus cultivation increased from 32,700 hm~2 in 1949 to 2.6 million hm~2 in 2015,which has increased by nearly 80 times in 60 years.With the adjustment of citrus industrialization structure and the improvement of mechanization level,the mechanization of citrus spraying has become more and more important in the citrus production process.In China,citrus is concentrated in mountainous and hilly areas.In order to improve the medicinal efficiency of citrus,reduce the cost of artificial pharmacy and increase the dosage,this paper has made a shaping orchard sprayer and adopts air spray technology to improve the ability of droplet penetration and the rate of effective deposition,etc.The main research contents of this paper are as follows:(1)Machine design and component selection,according to the spacing of citrus trees and the shape of fruit trees,the basic size design of the sprayer was conducted,which included the height and size design of the sprayer chassis and the design and trial production of the profiled sprayer bracket.The selection of parts includes the selection of nozzles and pumps,the determination of the volume of the pesticide box,the selection and trial production of axial fans,the layout and design of the transmission system,etc.,in order to achieve the purpose of compacting the structure and high quality of spraying.(2)The optimal parameters of air supply were determined.The effects of axial wind speed,air supply distance and air supply angle on the fog deposition effect were studied through experiments.Taking the amount of droplets deposited in the inner layer of fruit trees(ie,penetrability)and the uniformity of the droplets on the positive and negative sides of the leaves as the index,the best air supply parameters are tested in the case of satisfying the uniformity and penetrability of the droplet deposition.And the best consequence is that the speed of supply wind is 11.78m/s,the angle is 30°and the air supply distance is 0.25m.Under the condition of air supply,the common phenomenon of droplet drift at the top of the tree was studied.It was found that the top fan can effectively suppress the drift of the top droplet under the proper air supply angle(inclined downward air supply).(3)Under the condition of optimal air supply parameters,the characteristics of droplet deposition were studied on the profiled spray bar.According to the symmetry of the two-side application and the symmetry of the spray area of the nozzle,the spray flow field is simplified into a two-dimensional flow field.The CFD simulation software such as ICEM and FLUENT is used to simulate and compute the two-dimensional flow field of the contour spray.Finally,the motion characteristics of the droplets under different spray distances are obtained,including the velocity vector distribution of the droplets and the pressure distribution of the flow field,besides that the amount of drift and the amount of ground loss are calculated.(4)The functional test of the prototype was completed,which included the processing and debugging of the profiling-winding sprayer.Under the same conditions as the simulation conditions,the benchmark test of the whole machine was carried out to test the droplet deposition amount and ground loss of each droplet collector under different spray distances and the results were compared with the CFD model.It is concluded that the model can accurately simulate the droplet deposition characteristics within 1m from the nozzle.The error between the simulated droplet loss and the experimental droplet loss is maintained at less than 32%.Finally,the uniformity test of the droplet distribution in the vertical direction was carried out,and it was found that the droplets were distributed less in the bottom of the fruit trees,and the distribution uniformity in other parts of the fruit trees was better. |
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