无人机果树施药旋翼下洗气流场分布特征研究  

Distribution characteristics of rotor downwash airflow field under spraying on orchard using unmanned aerial vehicle

作　　者：张豪 祁力钧[1] 吴亚垒 程浈浈 刘婠婠 Elizabeth Musiu 肖雨 杨泽鹏 Zhang Hao;Qi Lijun;Wu Yalei;Cheng Zhenzhen;Liu Wanwan;Elizabeth Musiu;Xiao Yu;Yang Zepeng(College of Engineering,China Agricultural University,Beijing 100083,China)

机构地区：[1]中国农业大学工学院

出　　处：《农业工程学报》2019年第18期44-54,共11页Transactions of the Chinese Society of Agricultural Engineering

基　　金：科技部国家重点研发计划项目“现代果园智能化精细生产管理技术装备研发”(2017YFD0701400);科技部国家重点研发计划项目“地面与航空高工效施药技术及智能化装备(2016YFD0200700)”

摘　　要：植保无人机悬停果树施药时的旋翼下洗气流场分布对雾滴空间运动和在冠层内部的附着、穿透有重要影响。该文基于计算流体动力学(computational fluid dynamic,CFD)方法,结合RNGκ–ε湍流模型、多孔介质模型和滑移网格技术,通过构建虚拟果园,对六旋翼植保无人机悬停果树施药时的下洗气流流场进行数值模拟,分析在无人机不同悬停高度、不同果树生长阶段和不同自然风速下的气流场分布特征,并进行标记点下洗气流速度测试试验。研究结果表明:1)自然风速大于3m/s时,旋翼下洗气流速度已淹没于环境自然风速中,不再满足植保无人机悬停施药作业条件;2)自然风破坏了旋翼下洗气流的中心对称状态,向下风方向出现后扬,且随着自然风速和悬停高度的增大,后扬距离随之增大;3)与无自然风状态比较,果树生长时期对其喷头处速度分布影响不显著,主要受自然风影响,且竖直向下的z向气流占主体地位,对雾滴的对靶运输起主导作用,应将喷头安装于可使雾滴获得较大z向速度的旋翼正下方0.2m处附近;4)无人机悬停位置沿逆风方向调整后,冠层内部上、中、下层气流平均速度较调整前分别由1.36、0.80、0.81m/s增大至3.04、2.37、1.63m/s;上、下层速度分布变异系数分别由74.26%、35.80%降至45.39%和22.70%,中层略有增大,总体利于实现对靶喷雾。试验结果表明,标记点下洗气流速度测量值和模拟值之间具有较好的一致性。该文可为动态环境条件下植保无人机悬停果树施药的对靶喷雾自适应控制技术研究提供参考。when the plant protection unmanned aerial vehicle (UAV) is used to spray pesticides on orchard, the distribution of rotor downwash airflow filed has significant influence on the spatial movement of the droplet and the adhesion and penetration of the droplet inside the canopy. Based on computational fluid dynamics (CFD) method, combined with RNG κ-ε turbulence model, porous model and sliding mesh technology, the rotor downwash airflow field of a six–rotor plant protection UAV in hover when spraying on orchard was simulated. The simulation was done in the constructed virtual orchard. The characteristics of the airflow field were analyzed in different hovering heights of the UAV, fruit growth stages and natural wind speeds. Verification experiments were carried out through measuring the downwash airflow velocity at marked points. The results showed that: 1) it no longer met the conditions for spraying of the plant protection UAV in hover when the natural wind speed was greater than 3 m/s due to the downwash airflow under the rotor submerged in the natural wind of the environment. 2) Natural wind destroyed the central symmetry of downwash airflow of the rotor, and airflow diffusion appeared along the downwind direction. With the increase of natural wind speed and hovering height, the backward lift distance increased. When the hovering height was 3 m, and the natural wind speed was 1 and 2 m/s, the trailing distance of the rotor under the airflow reached 1 and 2 m respectively;when the natural wind speed was 3 m/s, the trailing distance had been more than 2 m. Under the condition of natural wind speed of 2 m/s, and the hovering height was 3 and 3.5 m, the trailing distances of the rotor under the airflow were not much different, both were both 2 m, but the former was in contact with the target canopy layer, and the latter was not in contact;When the hovering height was 4 m, the trailing distance of airflow had exceeded 2 m. 3) Compared with the state of no natural wind, the velocity distribution at the nozzle was

关 键 词：无人机 农药 模型 下洗气流 果树冠层 多孔介质 

分 类 号：S49[农业科学—植物保护] S25