Design And Experiment Of Three-Port Air-Assisted Variable Sprayer For Citrus Orchards

Citrus fruits are widely plant in China,and most of them are planted in hilly areas.The hilly citrus orchards are closed between rows,the garden has a certain slope,the turn of the monopoly head is narrow,while the fruit trees have dense foliage and uneven tree height.Orchard plant protection accounts for a large proportion of orchard management,which is the key link to ensure stable and increased fruit production.According to the modern standard citrus orchard garden construction planning and precise variable spraying needs.In order to improve the effective deposition rate of fog droplets inside and outside the canopy and the fog droplet atomization effect,a three-port air-assisted variable spraying machine for citrus orchards is designed,which has compact structure and small size.The main research elements are as follows:(1)An air-assisted variable sprayer is designed for the environment of standard citrus orchards on gentle slopes and hills.The air-assisted system,spraying system,crawler mobile chassis,automatic mixing device and electric control system are designed.And the mathematical model of spraying width and air delivery angle is proposed.(2)Design of key components of the sprayer.In order to reduce the influence of the slope of gently sloping hilly orchards on the attitude of the three-port nozzle,a nozzle attitude regulator is designed to realize variable spraying width and wind direction spraying operations.An automatic mixing device is designed to reduce the direct contact between farmers and pesticides for the problem of uneven mixing of oily pesticides and water.A three-port nozzle is developed according to the requirements of precise variable application,which enables each atomization nozzle to open and close independently to obtain a high outlet air speed and thus improve droplet penetration.(3)The computational fluid dynamics(CFD)simulation of the air volume distributor and the three-port nozzle is completed.The simulation results proved that the air delivery system of the sprayer met the expected design requirements,and the air outlet could produce a uniform and higher air velocity.Based on the size characteristics of citrus trees and the structure of the sprayer,the spray field calculation area model is established,and the spraying width of the sprayer is 2.24 m at 0° air supply angle.(4)The electric control system of the variable sprayer is designed to realize the remote control opening and closing of the atomization nozzle.Based on STM32 microcontroller to complete the remote control of the wind feeding angle.The crawler mobile chassis and sprayer spraying operation system are designed with independent electronic control circuits.(5)Prototype trial production and spraying experiment.The prototype of the threeport air-assisted variable sprayer is produced independently.The average droplet size of the sprayer is 97.490 μm and 90% of the droplets are less than 188.677 μm.Three sets of vertical distribution tests with different wind-feeding angles and nozzle openings are designed to obtain the spray height significantly affected by each atomizing nozzle and the effect of wind-feeding angle on the vertical deposition of droplets.The field deposition rate experiment is conducted under the working conditions of 0° and 20° for the upper and lower air supply angles,while the nozzles are opened and closed remotely according to the height of the citrus trees.The experiment results showed that the effective deposition rate of droplets is 53.699% and the average deposition ratio of inner and outer layers is 0.444.In this paper,a three-port air-assisted variable sprayer for citrus orchards is developed.The design and implementation of mechanical structure and electric control system are completed,and the simulation of air field and spray field is researched by CFD simulation.The deposition test of droplet particle size and vertical distribution is carried out in indoor environment,and the effective deposition rate test of the variable sprayer is carried out in the field environment.It can provide reference for the research of precision spraying technology and equipment in hilly orchards.