锥形风场式防飘喷雾装置内流道优化与防飘特性

锥形风场式防飘喷雾装置是利用辅助气流进行防飘作业的一种创新结构形式。为分析其防飘机理，改善防飘喷雾作业效果，对现有装置进行优化设计与防飘特性研究。基于质子动力学基本定律，构建了单个雾滴在运动空气介质中的受力模型，明晰了锥形风场的防飘机理。运用流体力学理论分析内流道气流损失，并利用CFD数值仿真技术结合风场测试对防飘喷雾装置进行优化设计。结果表明：当内流道弯管的曲率半径设计为4 cm时，优化后装置出口处仿真试验风速较优化前提高23.5%，测试试验风速较优化前提高28%，风机有效利用率提高21.2个百分点，优化方案合理。风洞条件下装置防飘特性试验结果表明：侧风风速、喷头高度、锥风风速与总雾滴飘移量占比具有相关性，通过多因素正交试验建立的竖直和水平方向的数学模型显著性较高（P<0.05，R2分别为0.934、0.945），表明锥形风场可以抵御绕流涡旋的产生，具有减少雾滴在纵向高度上随风飘失的特性。该研究可为综合分析雾滴飘移沉积规律提供一定参考。

Optimization of the inner flow channel of conical wind field anti-drift spray device and anti-drift characteristics

Abstract: An anti-drift sprayer with a conical wind field has emerged as an innovative structural device for the auxiliary airflow in plant protection operations during crop production. There is also a significant reduction of droplet loss for the effective deposition of fine particles in the target areas. However, an airflow obstruction can be found in the flow channel of the current sprayers, leading to the lower overall performance of the device. In this study, a systematic optimization was made on the inner flow channel in an anti-drift spray device under a conical wind field, thereby clarifying the anti-drift mechanism for better performance of the device. A force model of a single droplet was also constructed for the moving air medium, according to proton dynamics. After that, the CFD numerical simulation and wind field test were utilized to optimize the airflow loss in the inner runner for the better design of the device. The simulation result showed that the disturbance of eddy current was improved without the abnormality of local speed after optimization. Specifically, the conical wind speed at the outlet of the device still reached 17.00 m/s, increasing by 23.5%, compared with that before the optimization. The wind speed test showed that the effective utilization rate of the auxiliary airflow at the outlet of the device was 21.2% higher than that before the optimization, when the radius of curvature of the inner flow channel elbow was designed to be 4 cm, indicating that the optimization plan was feasible. Furthermore, there were significant correlations between the cross wind speed, nozzle height, conical wind speed, and the proportion of total droplet drift under wind tunnel conditions. By contrast, there was a negative correlation between the conical wind speed and the proportion of total droplet drift. More importantly, the proportion of the total droplet drift presented a downward trend, whereas, the adverse effect of the crosswind on the droplet deposition gradually decreased, with the increase of conical wind speed. Additionally, a multi-factor orthogonal experiment was carried out to establish the mathematical model of the total droplet drift ratio in the vertical/horizontal direction. It was found that the cone-shaped wind field significantly reduced the droplet loss in the space with the wind. There was also a higher significance of the vertical/horizontal mathematical model (P<0.05, R2=0.934/0.945). Consequently, the conical wind field can be widely expected to effectively resist the generation of vortexes, thereby reducing the droplet loss with the wind in the vertical height. This finding can also provide a sound reference for the comprehensive analysis of droplet migration and deposition in protected agriculture.