Research On The Effect Of Air Speed Of Orchard Air-assisted Sprayer On The Droplet Deposition And Distribution In Canopy

In China,the planting area of fruit trees is the first in the world.And chemical pesticide play a preventive role,the deposit and distribution of pesticide in the canopy has an important effect on the application.In view of the complex characteristics of fog drop deposition distribution in the fruit tree canopy,a caterpillar air-assisted spray test platform was designed in this paper.Based on the test platform,experimental research on fog drop deposition was carried out,providing data reference for the subsequent wind control method and spray effect evaluation.The main contents and conclusions are as follows:(1)A crawler air-assisted spray test platform was designed,mainly for the design of walking device,spray system and wind regulating system and the selection of key parts.The walking device adopts four-wheel belt crawler structure.The specific parameters of the chassis are designed in detail.The rated power of the driving motor is 11 k W based on the functional requirements.Combined with the spray volume demand and the structure of the test platform,kross type double spray nozzle with drip prevention was selected for the spray system to determine the capacity of the medicine box,and the rated power of 5.5 k W plunger pump was selected to provide power.The wind regulating system controls the fan speed and adjusts the wind speed of the outlet.The rated power of the supporting driving motor is 11 k W.The diesel generator set with 50 k W power is selected as the overall power of the spray test platform to provide sufficient power.(2)Carry out performance parameter test based on the air-borne spray test platform.First of all,the influence of spray pressure on the flow rate of the spray head of the air delivered atomizer was studied.The test results showed that the flow rate of the spray head gradually increased with the increase of pressure,and the change trend of spray volume of the spray head was basically the same under different pressure conditions.Secondly,the variation rule of airflow at different nozzle positions of the fan outlet was explored by changing the fan speed.The result is that the velocity at the air outlet increases with the increase of fan speed,and the velocity at the air outlet ranges from13.39 to 41.78 m/s.Then,the horizontal range of the sprayer under the conditions of wind spray and hydraulic spray is studied,which is 4.0 m and 4.8 m respectively.Finally,the effects of wind speed and spray distance on the distribution of droplet deposition in the vertical direction were studied.The experimental results show that the droplet deposition firstly increases and then decreases under different fan speeds,and the distribution position of the maximum droplet deposition in the vertical direction gradually increases.Within a certain range of fan speed,the influence of spray distance on droplet deposition decreases gradually with the increase of fan speed.(3)Based on the air-assisted spray test platform,experiments on the effect of airflow on the distribution of liquid deposition in the canopy chamber were carried out in laboratory and orchard environments.The optimal wind velocity range of simulated canopy was determined to be 18.12～37.05 m/s through spraying experiments at different airflow.Based on the optimal airflow range,a three-factor and five-level universal rotation orthogonal experiment was designed,and a quadratic universal rotation regression analysis was used to establish the calculation model of liquid medicine deposition per unit area at the inner,middle and outer positions of the fruit tree canopy.The model fitting coefficients were 81.99%,85.75% and 90.42%,respectively.The significance analysis of the test factors was conducted.The results show that the experimental factors have different effects on the deposition of liquid gas in the inner layer: spray distance > leaf area > airflow;the deposition of liquid gas in the middle layer: spray distance > airflow > leaf area.An orchard model validation test was carried out for peach trees.The test results showed that the calculation errors of the model in the outer,middle and inner parts of the canopy bore were 23.26%,22.38%and 32.62%,respectively.This study can provide data support for the evaluation of spraying effect and the selection of airflow of the orchard air spraying machine.