脉冲射流式水稻播种无人机一分四路分流装置设计与试验

Design and Testing of One-point-four-way Diversion Device for Pulse-jet Rice Seeding Drone

摘要:

脉冲射流式水稻播种方法通过将水稻芽种在射流液柱的裹挟下加压，提升种子的出射速度以减小外部旋翼风场的干扰，从而实现无人机机载方式的成行成穴播种。一分多路分流装置是提高脉冲射流式水稻播种机作业效率的重要部件。针对播种装置作业时的播种均匀性问题，围绕脉冲射流式播种物料的液固两相流（液态物料+芽种），以粤农丝苗稻种为对象，建立了一分四路分流装置的CFD-DEM耦合仿真模型；为了优选出适合脉冲射流式水稻播种液固两相流的分流方案，以分流装置类型（直分式轴端型、直分式中间型及锥分式分流）、入流出流轴线夹角作为因素，运用层次分析法构建了各出口流速、流量、出种均匀性变异系数及总压损失构成的分流均匀性综合评价指标，进行了两因素三水平正交仿真试验，试验结果表明，锥分式分流装置入流出流轴线夹角180°时，其分流均匀性综合评价指标为19.71%，表现出较优的分流均匀性；为了进一步优选一分四路分流装置的几何参数，探究了缩径段长度（Lr）、分流板与分流装置入口距离（Li）以及分流板长度（Lb）因素间交互作用对分流装置整体性能的影响，设计了三因素三水平正交仿真试验，响应面分析表明Lb影响最显著（Lb＞Lr＞Li），优选出的参数组合为Li=5mm、Lb=25mm、Lr=55mm（出口内径11.5mm，出口中心距30mm），分流均匀性综合评价指标为5.47%；制作了样机进行田间验证，试验结果表明，基于一分四路分流装置的脉冲射流式无人机播种作业，整机播种作业的总排种量稳定性变异系数在0.5%~0.7%间，种穴间的播种均匀性变异系数均低于40%，种行间播种均匀性变异系数均低于28%，田间验证试验的航线间总排量稳定性变异系数在0.27%以内，航线间总播种量均匀性变异系数为3.86%，符合GB/T 25418—2022标准，验证了装置在田间作业时的可行性。

Abstract:

The pulse-jet rice seeding method achieves rows and holes seeding in an unmanned aircraft airborne manner by pressurising the rice shoots under the wrapping of a jet liquid column, which enhances the seed ejection velocity to reduce the interference of the external rotor wind field. The one-point-multiplex diverter device is an important component to improve the operational efficiency of pulse-jet rice planter. Regarding the issue of seeding uniformity during the operation of seeding devices, focusing on the liquid-solid two-phase flow of pulse-jet seeding materials (liquid material with germ seeds), using Yuenongsimiao rice seeds as the subject. A CFD-DEM coupled simulation model of a one-in-four branch device was established;in order to select the optimal branching scheme suitable for the liquid-solid two-phase flow of pulsed jet rice seeding, based on the type of branching device (straight-split axial end-type, straight-split intermediate-type, and conical-split diversion), and the angle of the inlet and outlet axes were used as factors, and the hierarchical analysis method was employed to construct a diversion scheme. As a factor, the comprehensive evaluation indexes of diversion uniformity for each outlet flow rate, flow rate, coefficient of variation of outflow uniformity and total pressure loss were constructed by using hierarchical analysis method, and two-factor and three-level orthogonal simulation tests were carried out, and the test results showed that, when the angle of inlet and outlet axial clamping angle of the cone-type diversion device was 180°, the comprehensive evaluation indexes of its diversion uniformity was 19.71%, which showed a better diversion uniformity. In order to further optimize the geometrical parameters of the one-part-four-way diverter device, the effects of the interaction between the length of the reducing section (Lr), the distance between the manifold and the inlet of the shunt device (Li) and the length of the manifold (Lb) on the overall performance of the diverter device were explored, and a three-factor, three-level orthogonal simulation experiment was designed. The preferred parameter combinations were Li=5mm, Lb=25mm, Lr=55mm (outlet diameter 11.5mm, outlet centre distance 30mm), and the comprehensive evaluation index of diversion uniformity was 5.47%;a prototype machine was made for field verification, and the test results showed that the total seed displacement of the whole machine sowing operation of the pulsed jet unmanned drone sowing operation based on a one-point-four-way diversion device was within 0.5% of the stability coefficient of variation. The coefficient of variation of stability was between 0.5% and 0.7%, the coefficient of variation of sowing uniformity between seed holes was lower than 40%, and the coefficient of variation of sowing uniformity between seed rows was lower than 28%. The coefficient of variation of stability of the total discharge between routes of the field validation test was lower than 0.27%, and the coefficient of variation of the total sowing uniformity between routes was 3.86%, which was in line with the standard of GB/T 25418—2022, and it was in accordance with the standard of GB/T 25418—2022, and the device’s performance in the field operation was verified.