Simulation and experiment on single-channel and double-channel airflow field of orchard sprayer

Abstract: The spraying equipment and applied pesticide technology have been seriously lagging behind; the air-assisted orchard sprayer plays an important role in solving the problem. Compared with the traditional air-assisted spraying machine, the strong airflow from the draught fan of the tower-type spraying machine can convey the fog-drop by a large distance, and increase the penetrability and deposition of fungicide in canopy, so it has more outstanding performance. The existing research mainly focused on the target airflow field distribution, however, the problem that the airflow fields on the left and right sides are different due to the flow channel structure, is often ignored. In view of the phenomenon that the airflow field and drug delivery are nonuniform on the left and right sides of the single-duct orchard sprayer, the self-manufactured double-duct air-assisted test-bed in orchard was designed. This article adopted the methods of computational fluid dynamics (CFD) numerical simulation and experiment, made a comparative and analytic research on the single- channel and double-channel drug delivery from the inside out, and analyzed the internal flow field distribution of the single-channel and dual-channel with the viscous-standard model, in order to verify the accuracy of the numerical simulation through the fitting analysis of simulative value and test value. Based upon the Golden software Voxler fitting processing and weighted analysis on the wind speed scatter data at air outlet and different cross sections from air outlet, the article analyzed the characteristics of the single and double duct. The results showed that: for single duct, the inner flow field was stronger on the right side than that on the left side, while for double duct, the inner flow field was almost the same on both sides. The wind speed of double duct at air outlet was stronger than that of single duct, and the directions of wind speed curves on both sides of double duct were basically the same. According to the airflow distribution pattern in external airflow field above the cross sections which were 0, 1, 2, 3, 4 and 5 m from the air outlet on both sides, it was found that the airflow field concentration area had an obvious shift, and there was a big difference of airflow field intensity between both sides for the single duct, while the wind filed was almost fundamentally symmetric on both sides for the double duct. As for the central symmetry, the weighted averages of the maximum wind speed to the center distance were respectively -3.23 and -1.33 on the left and right side in double duct on the cross section 2 m from air outlet, and they were respectively -24.99 and -32.33 in the single duct; at the same time, with the increase of the distance, the shift from the center in the double duct became smaller than that in the single duct. After comprehensive analysis, it can be concluded that the double duct airflow field has comparative advantages over the single flow channel in the aspects of bilateral symmetry and central symmetry. The research can provide a reference for further optimization of air-assisted spraying technology.