基于多旋翼植保无人机的耦合风场对前飞喷雾分布影响机理研究

Multi-rotor plant protection unmanned aerial vehicle spraying is an important development direction of aviation efficient plant protection technology. However, the wind flow condition of spraying forward operation is complex, the influence mechanism of the coupling wind field on the movement of droplets is also unclear, which restrict the effective improvement of the distribution quality. In this project, taking the relationship between coupled wind field and spraying deposition distribution of the multi-rotor plant protection unmanned aerial vehicle spraying forward as the studying object. Combining with the coupled wind field simulation platform test, determination of droplet distribution and high speed photography image analysis, the influence mechanism of the coupling wind field on the sedimentary distribution will be elucidated. On the basis of wind fields computational fluid dynamics modeling, two phase flow modeling based on Lagrange description, and spraying forward attitude emersion by coupling solution of wind field and 6DOF program, the evolution process of vortex structure in coupled wind field will be ascertained; the intrinsic relevance between droplet motion behavior, droplet sedimentary distribution and coupled wind field will also be revealed according to the perspective of the kinematics of droplets. On this basis, the mathematical model of coupled wind field and spray distribution prediction will be established, combining with the experimental design method. Taking the uniformity of droplet distribution as the objective, the range of operating parameters which meet the deposition quality will be explored, the design criteria for the parameters of spray bar will also be presented. This project will provide the theoretical basis for the design of environmentally friendly and efficient multi-rotor plant protection unmanned aerial vehicle.

多旋翼植保无人机是航空高效植保装备的重要发展方向之一，但前飞喷雾作业风场流动条件复杂，耦合风场对雾滴群运动分布的作用机理尚不明晰，制约着喷雾作业沉积分布品质的有效提高。以多旋翼植保无人机前飞耦合风场与喷雾沉积分布关系作为研究对象，融合风场组合测试平台试验、雾滴沉积分布测定及高速摄影图像分析等试验方法，阐明前飞作业耦合风场对喷雾分布形态的影响机理；通过风场的流体动力学建模、基于雾滴拉格朗日描述的两相流建模、流场和6DOF算法耦合计算复现前飞作业姿态等理论方法，探明耦合风场涡系结构的演化过程，从药液雾滴群运动学的角度出发，揭示耦合风场与药液雾滴群运动行为、沉积分布的内在关联性；以此为基础，并结合试验设计方法，建立耦合风场与喷雾分布预测的数学模型，以雾滴分布均匀性为目标，探讨满足沉积品质的作业参数包络，提出喷杆结构参数的设计准则，为设计环保、高效的多旋翼植保无人机装备提供理论依据。

多旋翼植保无人机是航空高效植保装备的重要发展方向之一，但前飞喷雾作业风场流动条件复杂，耦合风场对雾滴群运动分布的作用机理尚不明晰，制约着喷雾作业沉积分布品质的有效提高。首先，针对航空施药模式下喷头喷雾参数与雾化参数关系不明确的问题，结合喷雾性能测试建立代理数学模型，讨论了CN1215型航空专用离心喷头主要工作参数对雾滴体积中径（Dv50）、喷幅的影响规律。其次，针对多旋翼无人植保机，采用Optimscan5-2015011K05型扫描仪对旋翼等关键部件进行三维扫描，实现无人机的逆向重构；基于雷诺平均N-S方程及Realizable k-ε湍流模型，引入动网格技术，建立了不同载荷悬停状态的下洗气流演化三维数值计算模型，结合风场测试和数值模拟研究了多旋翼无人植保机下洗风场的发展演化分布规律、及载药量对悬停状态下的风场影响机理。第三，引入雾滴离散相，并对连续相进行动量、能量方程修正，建立喷头含雾滴离散相的两相流模型，结合喷头喷幅测试试验验证了含雾滴离散相的两相流模型计算雾滴运动轨迹的可行性与有效性；建立了多旋翼植保无人机悬停喷雾条件下含雾滴离散相的三维两相流模型，分析了下洗气流对雾滴运动规律及分布规律的影响，结合数值仿真计算边界可设置的优势，进一步讨论了粒径对雾滴在下洗风场扰动下的运动、沉积规律。第四，针对旋翼下洗气流对棉花叶片背面雾滴沉积数量促进效果不明显的问题，通过计算流体动力学方法（CFD）对无人机不同作业速度下雾滴流主要沉积区域进行仿真；结果发现，冠层扰动区域和雾滴流沉积区域不同步是旋翼下洗气流未明显改善棉花叶片背面雾滴沉积数量的主要原因；从硬件和软件两个方面研究设计了无人机喷头倾角自动调节系统，通过田间试验验证该系统的喷洒性能，结果表明安装该系统后叶片正面和背面雾滴沉积数量均明显增加。最后，限于计算量的限制，针对影响雾滴飘移的几个重要因素，结合优化拉丁超立方试验设计、径向基神经网络方法及计算流体力学数值计算技术建立多旋翼植保无人机喷雾飘移的高效显式近似模型，实现对施药飘移情况的初步预测。