| Efficient control of fruit tree diseases and insect pests is an important part of orchard production management.With the rapid development of China's modern large-scale wide-row dense planting orchards,tower-type sprayers have been used more.This type of sprayer is a high-efficiency spraying machine that uses the airflow of fan to blow mist droplets through the outlet of multiple air ducts.It can make droplets penetrate the canopy of fruit trees,and realize low-volume spraying.However,due to the high height of the diversion duct,the problem of uneven air speed at each outlet generally exists,which affects the spray quality.The internal flow field of the pneumatic system is a key factor in determining its air speed at outlet.The rational arrangement and design of key structures and parameters such as fans,baffles,and deflectors have an important role in improving its spray effect and quality.By investigating the cultivation characteristic parameters of China's apple and other fruit trees that used wide-row dense planting,combined with the large-scale orchard's high-efficiency plant protection agronomic needs,a three-dimensional digital prototype model of the tower-type sprayer and its pneumatic system was established using AIP software to verify the model's assembly.Combined with the prototype production of the sprayer and the uniformity detection test of the air speed at outlet,the simulation model of the air flow field inside the tower-type sprayer was established,and the CFD numerical simulation test was carried out.By setting the monitoring points of the outlet,the simulated values of the air speed of each outlet of the sprayer were obtained,and the benchmark and linear correlation fitting analysis were performed with the actual measured values of the prototype test,and the goodness of fit was calculated to be 0.8689.The model can be used for subsequent calculations.Use CFD technology to compare and analyze the distribution effects of different air flow fields of the sprayer,and optimize the overall layout of the pneumatic system.Orthogonal experiments were designed with the air speed of the inlet,the installation position of the fan,the installation angle of the inner partition,the length and the installation angle of the deflector as the deciding factor,and the standard deviation of the air speed at the outlet as the evaluation index.By comprehensively analyzing the calculation results of each set of orthogonal test models and comparing the uniformity of the air speed distribution of each outlet of the sprayer model,the overall structure of the pneumatic system of the tower-type sprayer was determined,so that the uniformity of the air speed distribution of each outlet of the sprayer reached the standard.The Standard Deviation of the air speed at each outlet is 4.33.When this scheme is adopted,the inlet air speed of the sprayer is reduced from 20m/s to 12m/s,which reduces energy consumption.The verification test results show that the simulation calculation results are correct,which provides a theoretical basis and data support for the structural optimization of the pneumatic system.The method of combining simulation calculation and experimental research is used to optimize the pneumatic system of the tower-type sprayer.The uniformity of the flow field distribution at the outlet of the sprayer is improved.The transmission of the air flow inside the sprayer is improved.And the sprayer after optimized was tested.The test results show that the coefficients of variation of the three layers of fruit trees.are 27.56%,23.64%,21.95%,the average droplet deposition density is 141 grain/cm2,the droplet adhesion rate is 67.59%.The spray performance index reaches the orchard spray operation quality standard. |
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