Air-assisted Sprayer Of Traditional Apple Orchard Based On CFD Simulation

Plant protection technology is one of the rapid and most effective ways to ensure the yield of fruit trees.At present,the high efficiency sprayer is dominated by large explosive devices,but the large explosive devices are difficult to enter the traditional apple orchard.Therefore,most of Chinese traditional orchards are still sprayed with human-powered or stretcher sprayers.However,the above spraying application method has resulted in uneven application,environmental pollution,drug residues,and higher labor intensity.At the meantime,the traditional method of developing the sprayer has long producing cycle and high costs.CFD(Computational Fluid Dynamics)technology were adopted as the theoretical basis for the development and control of sprayers so as to decrease the time and cost.To develop an air-feeding sprayer that suitable for Chinese orchards,the research develops an air-feeding sprayer suitable for Chinese traditional orchard based on CFD technology.The main research conclusions of this thesis are as follows:Firstly,the simulation of internal and external flow fields of sprayer based on CFD.The air-assisted sprayer in tradition requires higher cost and longer cycle of development.To reduce the cost the most important component of the air conveying system in air-assisted sprayer,was designed and optimized based on CFD technology.Further,based on the principle of minimizing the energy loss and the vortex of airflow and maximizing the uniformity of flow distribution,the research determined the optimized structure and specific parameter of the bellows.In addition,this paper also simulated and analyzed the distribution of flow field in the sprayer,and then established the model between spray height and nozzle inclination.The relationships of the spray height and nozzle inclination based on the model are as follows: when the nozzle inclination is greater than 85° or less than 40°,there is little effect on the change of airflow field;when the nozzle inclination is 40°-85°,the spraying height is basically linear with the nozzle inclination,and increased with the increase of nozzle inclination.Secondly,the design of air-assisted sprayer applied in apple orchard.Combining the development status of sprayers,the results of flow field simulation and the different planting patterns in traditional apple orchards in China,the research described an air-assisted sprayer suitable for traditional apple orchard.The air conveying system,spray system,transmission system and main components of the air-assisted sprayer were designed,and then the chassis of air-assisted sprayer,the bracket of pesticide box and the axle were theoretically analyzed,optimized,and improved.In addition,the research also took a lightweight optimization design to the chassis of air-assisted sprayer and the bracket of pesticide box in the premise of ensuring safety,reliability and stability.Thirdly,the droplet distribution test and field passing test of the sprayer.I designed the field test of the sprayer droplet coverage and penetration.The results showed that the air sprayer has a high droplet coverage and a uniform droplet distribution.Achieving the same spraying situation,the spray amount is only 15 % of the stretcher sprayer,but the working efficiency is 10.8 times higher that of the stretcher sprayer.During the tests of the sewer-passability,obstacle-passability,and climbing-passability,the air-assisted sprayer showed good performence when full loaded.Lastly,the influence of different speed on the drift of flow field based on CFD simulation.The distribution of the flow field is significantly affected by the speed of the sprayer.In order to figure out the distribution law of the flow field at different speed,The CFD dynamic grid technology were used to study the influence of different speed on the drift of the sprayer in the three-dimensional model,and the distribution and drift law of flow field at different speed.A relationship model between the drift distance of the flow field and the vehicle speed has been established to provide theoretical basis for automatic control of the sprayer and efficient target setting.The simulation shows that when the speed is about 0.5 m/s to 2.0 m/s,drift distance is gradually increasing as the speed increases,but the growth rate is from positive to negative.