【作者】 张铁；

【导师】 杨学军；

【作者基本信息】 中国农业机械化科学研究院 ， 机械设计及理论， 2012， 博士

【摘要】 长期以来,我国玉米、甘蔗等高秆作物生长中后期病虫害防治难的问题一直没有得到解决。因此,研究高秆作物植保作业机械和防飘移技术对发展我国农药药械与施药技术有一定的理论意义,对高秆作物生长期全程病虫害高效防治具有一定的实用价值。本文根据国家高技术研究发展计划(863计划)项目课题“高秆作物高效施药技术研究与装备创制”(课题编号：2008AA100901)研究任务,结合项目研制的3WZC-2000型超高地隙自走式喷杆喷雾机,对高穿透性风幕系统进行了实验、设计和性能优化,对风幕式高穿透施药技术在高秆作物施药作业过程中雾滴的沉积分布特性和飘移规律进行了试验研究和CFD仿真分析。设计了风量(风速)和气流方向可调的新型风幕系统,能够进行风幕系统作业参数的实时调整,提高农药有效利用率,减少环境污染。建立了风幕系统的风幕结构基于k-ε标准湍流模型的气流场速度分布模拟模型,并对风幕结构进行了优化设计。改进后的风幕系统出口气流速度增加,辅助气流沿喷杆方向分布均匀性良好,风幕系统性能得到了大幅提高。在玉米生长高度分别为0.8、1.6和2.2m时对超高地隙喷杆喷雾机风幕式高穿透施药技术进行了田间试验,研究了喷雾压力、喷雾机作业速度、风幕出口风速及植物冠层特性对雾滴沉积量和分布均匀性的影响,论证分析了风幕系统的防飘效果和农药利用率使用效果。田间试验结果表明,超高地隙喷杆喷雾机风幕系统提供的辅助气流具有较强的穿透性,在施药作业过程中对增加高秆作物枝冠中下层的雾滴沉积特性具有显著作用;风幕系统的辅助气流速度大小与雾滴沉积分布均匀性呈正相关系,风幕出口风速越大,雾滴沉积分布均匀性越好,雾滴穿透性越强；在相同的作业条件下,增大喷雾压力使雾滴在冠层的单位面积沉积量增加,而对雾滴的分布均匀性无明显影响；在所研究的影响雾滴沉积量和分布均匀性的4个因素中,风幕出口风速是雾滴沉积分布均匀程度的决定因素,其次是植物冠层特性和喷雾压力,而喷雾机作业速度对其影响最小；超高地隙自走式喷杆喷雾机风幕系统能够有效的减少雾滴飘移,提高农药的使用效率。结合超高地隙喷雾机实际结构,应用计算流体力学软件Ansys Fluent,采用离散相模型、标准k-ε湍流模型与Couple算法,建立了风幕式高穿透施药技术雾滴沉积飘移分布模型。利用中心组合设计法设计模拟实验,重点对飘移率及其与影响因素之间的关系进行了仿真研究,确定了不同风机转速下雾滴飘移率与其各影响因素之间的函数关系,并利用试验对模拟研究结果的准确性进行了验证。结果表明,所建模拟模型能够比较准确的反映风幕系统各作业参数对雾滴飘移率的影响规律。基于响应曲面法对影响雾滴飘移的各参数进行了优化。确定了在风力等级为1、2、3、4级的作业条件下,获得较小雾滴飘移率时风机转速、辅助气流角度、喷头水平安装位置的合理取值范围。更多还原

【Abstract】 Pest control for high-stalk crops, like corn and sugarcane, at their middle and late growing stages, has remained a problem over years in China. It is therefore of great theoretical and practical value to study anti-drift technology of pesticide droplets for the development of crop protection equipment and effective application practice for pest control over the entire growth period of high-stalk crops.This study is part of the Study on Efficient Application of Pesticide and Development of Sprayer for High-stalk Crops (project number:2008AA100901), a project funded under the National High-Tech R&D Program (or863Program). Experiment, design and performance optimization of a high-penetrable air-assisted system were conducted on super-high clearance self-propelled boom sprayer, modeled3WZC-2000, developed through the project. Experimental study and CFD simulation were focused on the distribution characteristics of deposited droplet and the law of droplet drift during the application of pesticide in high-stalk crops with the high-penetrable air-assisted system.A new type of air-assisted system was designed with the speed and direction of air flow adjustable so that the operational parameters could be regulated in real time for improved pesticide utilization and reduced environmental pollution.Simulating model of air-velocity distribution of air-assisted system was developed based on the standard k-ε turbulent model, then the structure of air-assisted system was optimized, As a result, the optimized exit flow speed of the air-assisted system was increased, and the assisted air flow was uniformly distributed along the direction of boom, resulting in improved system performance.Field experiments were conducted on the pesticide application technology of high penetration in the super-high clearance boom sprayer at the corn height of0.8m,1.6m and2.2m respectively, in order to study the influence of spraying pressure, working speed of sprayer, air speed at the outlet of air-assisted system, and characteristics of plant canopy on the deposit rate and the uniformity in distribution of droplets. The system performance in anti-drift and pesticide utilization was analyzed.The results of field experiments showed that the assisted air flow from air-assisted system on the super-high clearance boom sprayer had a strong penetrability by evidence that the droplets deposited on the middle and lower plant canopy of high-stalk crops increased significantly during the pesticide application; the assisted air speed was positively correlated to the distribution uniformity of droplets deposited. The higher the speed of air at the outlet of the system was, the more uniform the deposited droplet was distributed and the stronger the penetrability of droplets was; Given that all the working conditions remained unchanged, the deposition of droplets on unit canopy area would be increased with the spraying pressure, while the uniformity of droplet distribution did not vary obviously. Among the four factors that affected droplet deposition and uniformity of droplet distribution, the air speed at the outlet of the air-assisted system played a determinant role, followed by canopy characteristic, spray pressure and working speed of the sprayer. The air-assisted system of the super-high clearance boom sprayer had been proven to be highly effective in controlling the droplet drift and improving the pesticide utilization efficiency.A droplet deposition and drift distribution model was established for high-penetration air-assisted pesticide application in accordance with the actual structure of the sprayer, using the CFD software Ansys Fluent, adopting the Discrete Phase Model (DPM), standard k-ε turbulence model and Couple algorithm. The simulation test was designed using Central Composite Design to study the relationship of drift rate with its influencing factors. The functional relation of droplet drift rate with its influencing factors at different rotation speed of blower fan was established and the accuracy of the simulation result was validated, indicating that the model was well fitted.In order to achieve the least droplet drift, reasonable value ranges were worked out for the rotation speed of blower fan, the angle of air-assisted flow and the horizontal installation position of spray nozzles at the Beaufort wind scale1,2,3and4, respectively.更多还原