Research On Double Fans Double Channel Orchard Sprayer Airflow Field Characteristic

The air-assisted spraying technique is becoming increasingly wider in the orchard spray operation and droplets can be driven by the high-speed airflow from the draught fan, which can adhere to different parts of fruits trees, saving the time and effort. The liquid is easier to be deposited on the internal of trees under the airflow blows. It can increase the fog-drop penetrability and the pesticide efficacy can reach 30%-40%, so that to solve the problems including orchard pesticide difficulty, pesticide application equipment backward, and low pesticide utilization rate. At present, the axial flow fan are the air supply of most air-assisted sprayers in orchard. Directional rotation of axial flow fan makes that the wind on one side is up, and the other side is down. The wind field asymmetry on both sides causes the inconsistent of distribution and the fruit tree pest control effect is also not the same on both sides.This passage is mainly based on the asymmetry of the spray on both sides of orchard sprayer and a double fan flow orchard is designed. The thesis uses the numeral simulation software Fluent to simulate the internal flow field of single and double fan flow channel and analyze the intrinsic factors that airflow field generate. Combined with wind speed data of external wind scatter measured in experiment, we can make a specific analysis of the single and double fan flow on the wind field,aiming to explore distribution regularity of airflow field of the double fan flow. In this thesis, the main research contents and relevant conclusions are as follows:(1)According to the orchard planting patterns in our country and the existing air-assisted sprayer in orchard, the tower-type double fan flow test bed is designed. The fan type structures with R + S level and a diameter of 660 mm. The fan blade number is 9 and rear guide vane number is 11. At the same time, some detachable parts are designed for single and double channel conversion to make a comparison with single and double fan runner wind field characteristics,. Wind field superposition area with the width of 0.1m was settled on the left and right sides of the double fan flow channel and wind filed at the air outlet shows the stacking effect, which can make a comparative study with the single fan flow wind field and establish the premise condition for the study of the wind field characteristics of two kinds air channel.(2)Make a numerical simulation analysis for the single and double fan flow channel. Study the airflow field condition of single and double fan flow channel by using computational fluid dynamics software Fluent and describe their inner flow field in detail. After comparative analysis on the simulation, the obvious asymmetry phenomenon could be found on both sides of the wind field produced by the single fan flow and it was stronger in the left side than that in the right side. However,both sides of the wild filed was basically symmetrical for double fan flow, because there was strong and weak, weak and strong superposition at the air outlet. Wind field was relatively consistent on both sides after the wind field complement.(3)Measurement result of wind speed at the air outlet shows that, for the double fan flow channel,when the fan speed reached 1600r/min, the max wind speed was 24m/s; when the fan speed reached1400r/min, the max wind speed was 21m/s and the max wind speed appears at the third sprayer position.However, there is much difference between the wind speed on the left and right side for the single fan flow channel and the wind speed trend is different either. In comparison, the wind speed symmetry is better for double fan flow channel than that of the single fan flow channel.(4)Make a measure for the scatter wind field speed of external specified points at the wind field by using wind speed measuring instrument and deal with the measured scatter data by using of Golden software voxler 3 to make the wind speed slice cloud atlas of the external wind field of both kinds of duct. According to make the analysis and comparison of cloud atlas for the single fan flow and double fan flow, it came to the conclusion that there was obvious asymmetry phenomenon on two sides of the single fan flow wind field and the left wind field is stronger than the right side wind filed. However, the double flow wind filed was basically symmetric distributed. At the 2m to 3m of double fan flow, the wind field distribution was that the wind power in the middle is stronger than that on the top and bottom,which can be well-matched with the fruit tree canopy height and meet the orchard pesticide wind send requirement.(5)Using weighting method can get the wind field offset situation about the center surface. When the draught fan was at the speed of 1600r/min and the double fan flow channel was at about 2 m, the weighted average at the left and right side is-3.23 and-1.33 respectively, that of the single fan flow channel is-24.99、-32.33 respectively. When the draught fan was at the speed of 1400r/min and the double fan flow channel was at about 2m, the weighted average at the left and right side is-2.15 and-6.17 respectively, that of the single fan flow channel is-25.28 and-29.77 respectively. As the growing distance from the air outlet, the double fan flow wind field weighted average grows slowly, that is to say,the double fan flow channel centering is better than that of the single fan flow channel.