受多通道气流作用的果树风送式变量施药流场仿形分布机理与控制策略

Air-assisted variable-rate spraying is one of the most important technologies for improving the effects of spraying and reducing pesticide doses. The current method of variable spraying is confined to a “tree to tree” pattern, whereas the tree canopy itself is irregular in shape and size. Therefore, the air flow rate and pesticide dose will vary on different sections of the tree canopy. The aims of this project were (1) to investigate air velocity and spray volume profiles under various working conditions of a multi-channel sprayer; (2) to clearly identify parameter adjustment strategies of a multi-channel sprayer, appropriate for detected tree canopies with different characteristics. The objectives of the project can be described as follows: (1) based on the multi-channel sprayer, to investigate the longitudinal and transverse attenuation distribution of air velocity with air spouts directed in the horizontal direction, and to establish a function defining the relationship between air velocity and position coordinates using free turbulent jet theory; (2) to determine the relationship between air spout direction, air velocity magnitude, and air velocity profile; (3) to investigate the relationship between nozzle direction, spray volume, and air-droplet flow profile; (4) to establish the parameter adjustment strategies for a multi-channel sprayer in order to create an air-droplet flow profile that is coincident with the detected shape and size characteristics of tree canopies. This project provides theoretical support and parameter adjustment strategies for the design and parameter optimization of an air-assisted sprayer.

风送式变量施药技术是果园农药增效减施的重要技术措施之一。当前变量喷施仅存在于“树与树”之间，而冠层本身作为一个不规则体，各区域所需要的气流、药量也不一样。针对靶标特征量化描述及需风、药特性不明，气雾流场仿形调节规律尚不清晰等现状，本项目从冠层不规则特征及风速、药量需求特性出发，以空气射流特性与施药技术理论为基础，深入研究气、雾流多通道施药技术，探寻多通道风送喷雾机不同工况下气流速度的纵向衰减及沿横向分布等特性，构建风速与空间位置之间的函数关系；在此基础上，重点研究各通道出风角度、速度和靶标仿形气流场形成之间的关系规律；多通道气流作用下，喷头流量、角度组合参数对靶标仿形雾流场形成的影响规律，探索靶标轮廓特征信息输入，施药参数输出的控制策略。该研究为果园风送喷雾机设计与参数匹配提供理论支撑与控制策略。

本项目从冠层不规则特征出发，以空气射流特性与施药技术理论为基础，深入研究气、雾流多通道施药技术，重点研究了多通道风送雾化装置设计理论与方法，开展了多通道风送式喷雾机、雾化器及后盖弧形罩结构优化及试验研究，继而探明了多通道施药喷施角度、间距等参数对果树靶标仿形气、雾流场影响规律，完成了果园多通道风送喷雾机气流场仿真与试验验证研究，研究了多通道风送喷雾机不同工况下气流速度的纵向衰减及沿横向分布等特性。.1）提出了受多股射流作用的仿形化施药要求，明确了多通道风送雾化装置设计理论与方法，并将多通道风送雾化装置设计理论与方法充分应用，开发了多通道风送雾化器及其关键部件、多通道风送雾化器试验台、多通道风送喷雾机等装置。.2）提出多通道风送系统射流特性的基本准则，明晰受多通道气流作用的雾量空间垂直分布特性，量化参数关系得到果园多通道风送施药气流运动特性及气流场空间分布一些基础理论与普适规律。.3）求得针对不同冠径区域的适宜风速、药量参数值，实现基于靶标轮廓特征的风、雾场仿形化调控，提出了代表冠层特征的施药参数组合控制策略。.项目研究结果中相关结论及数据能够对果园风送施药装备的研发及改进有一定的借鉴与促进作用。