植保无人机旋翼下洗气流对喷幅的影响研究

基于XV-2植保无人机,利用流体仿真,探究了该无人机旋翼下洗气流的速度分布特性。在此基础上,分析了在下洗气流影响下的雾滴运动方式,并进行实地测试。仿真分析说明:旋翼下洗气流从中心向外的流速差使流场从上向下有向外的铺展效应,使得喷幅增大,且喷幅与飞行高度成正比;旋翼外沿的卷扬气流使得喷幅范围内的雾滴沉积数出现2个峰值。试验结果表明:当飞行高度为6 m时,有效喷幅为10 m;飞行高度8 m时,有效喷幅为12 m。2种飞行高度下的雾滴分布均匀性基本一致。试验结果与仿真结果基本一致。研究结果可为无人机喷雾系统设计和航空植保作业参数的选择提供参考依据。

Influence of UAV Rotor Down-wash Airflow on Spray Width

The movement patterns of droplets on a UAV spray platform are quite different from those on a ground spray system because of its height from the target plants and the influence of the down-wash airflow. Few publications have mentioned how the UAV flying height influenced the spray width. Based on XV-2 UAV, by means of flow simulation and iteration calculation and experiments, the velocity characteristics of the rotor down-wash airflow and the movement patterns of droplets as influenced by the down-wash airflow were analyzed. The simulation results revealed that the velocity discrepancy from the middle to the outwards of the down-wash airflow led to an expanding tendency of airflow and thus an expansion of the spraying width. The spraying width was basically proportional to the flying height. The curling airflow around the rotor led to two peak values of droplet deposition within the spray width, which might also lead to an increase of spray drift. The experiment result showed that the effective spray width was 10m at a flying height of 6m and 12m at a flying height of 8m. The uniformities of deposition distribution were almost the same between each flying height. Considering the uniformities of deposition distribution, efficient spray deposition, spray drift caused by cross wind and injury of plants caused by down-wash airflow, the flying height of the UAV should be correctly chosen from a proper range based on its type and load. The experiment result was consistent with the simulation result. Therefore, the research result explained the influence of UAV rotor down-wash airflow on spray width and it can provide reference for the design of UAV spraying system and the choice of working parameters of UAV spraying.