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101.
A. Melese Endalew C. Debaer J. Vercammen H. Ramon P. Verboven 《Computers and Electronics in Agriculture》2010,71(2):128-136
The current trend in modelling flow phenomena within trees such as in orchards follows the assumption of the space occupied by the trees as a porous and horizontally homogeneous medium to avoid the flow details associated with the individual plants. This being sufficient at a larger field or regional scale much has to be done at a plant scale to analyse the flow details within the plant and its elements especially for sensitive agricultural operations such as spraying. This article presents an integrated 3D computational fluid dynamics (CFD) model of airflow from a two-fan air-assisted cross-flow orchard sprayer through non-leafed orchard pear trees of 3 m average height. In this model the effect of the solid part of the canopy on airflow was modelled by directly introducing the actual 3D architecture of the canopy into the CFD model. The effect of small canopy parts, such as very short and thin branches and flowers that were not incorporated in the geometrical model, on airflow was simulated by introducing source-sink terms in the Reynolds averaged Navier-Stokes (RANS) momentum and k-? turbulence equations in a sub-domain created around the branches. This model was implemented in a CFD code of ANSYS-CFX-11.0 (ANSYS, Inc., Canonsburg, PA, USA). In this work it was possible to link the real 3D architecture of pear canopy into a CFD code of CFX. The model was able to capture the local effects of the canopy and its parts on wind and sprayer airflow directly by inserting the tree structure into the model which gave realistic results. The model showed that within the injection region of the sprayer there was an average reduction of the jet velocity by 1 m s−1 for a distance of 2.3 m from the sprayer outlet due to the presence of leafless pear canopy. This reduction was variable at different vertical positions due to the difference in the canopy density. Maximal effect of the canopy was observed in the middle height of the trees between 0.25 m and 2.5 m which is the denser region with a bunch of several branches. The maximum velocity difference observed between these two positions was 1.35 m s−1 at 1.75 m height. Thus, regions of high and low air velocity zones of the sprayer due to the variable branch density of the pear tree were predicted. The effects of wind speed and direction on the air jet from the sprayer were investigated using the model. For a cross- (direction of 90°) wind speed of 5 m s−1 there was about 2 m s−1 reduction in the sprayer jet velocity at the jet centre and 0.5 m horizontal shift of the jet centre towards the wind direction. Generally there was a decrease in the jet velocity with increasing cross-wind and decreasing wind direction with respect to the jet direction. 相似文献
102.
【目的】基于复杂农林环境对喷雾机底盘的柔性化和智能化需求,提出了底盘概念设计方案生成和评价方法,为喷雾机底盘概念设计提供方法和理论指导。【方法】在对喷雾机底盘进行功能需求分析的基础上,以功能树形式对底盘进行了功能分解,采用机构综合法对喷雾机底盘分功能原理解进行了创新和综合,并构建底盘形态学矩阵;在集合专家经验的基础上剔除明显不合理的方案解;采用基于模糊数互补判断矩阵的群决策方法进行方案的评价,构建目标规划的数学模型并进行求解,最终确定最佳的设计方案。【结果】获得了喷雾机底盘分功能的多个原理解,其中主要检测功能原理解方案数为25个,主要执行功能原理解方案数为19 683个,经过筛选和综合评定,获得喷雾机底盘整体可行的概念设计方案有3种,经过专家评判,构造模糊区间数互补判断矩阵,通过求解得其排序权重分别为0.27,0.46,0.27,最终确定方案2为最佳方案,即以柴油机作为原动机为液压泵提供动力,驱动车轮马达完成四轮驱动及两轮转向功能;驱动液压缸完成底盘轮距、地隙调整和喷雾系统升降功能;驱动液压马达经圆柱齿轮和圆锥齿轮机构完成底盘工作台旋转功能;借助GPS和电子罗盘完成检测功能。【结论】借助功能原理分析和机构综合法可快速有效生成喷雾机底盘概念设计方案,基于模糊互补判断矩阵的群决策方法可有效消除个人主观偏好对概念设计方案评价结果的影响,这些方法可为喷雾机底盘乃至其他机械产品的概念设计提供理论指导。 相似文献
103.
介绍了 6HY - 2 0型烟雾机的技术性能及其在防治马尾松毛虫、刚竹毒蛾等森林主要害虫的效果 ,试验表明 ,6HY -2 0型烟雾机在不同郁闭度的林分中对森林虫害的防治效果可达 90 %以上 ,该机可在我省防治森林虫害中推广应用 相似文献
104.
Site Specific Weed Control in Winter Wheat 总被引：3，自引：0，他引：3
R. Gerhards M. Sökefeld K. Schulze-Lohne D. A. Mortensen W. Kühbauch 《Journal of Agronomy and Crop Science》1997,178(4):219-225
Field experiments were conducted in two winter wheat fields to assess weed control and quantify the amount of herbicide applied with a GIS map-based patch sprayer. Site specific weed management decisions were based on previously acquired weed distribution maps and an economic weed threshold model. A weed treatment map (on-off) was generated and georeferenced to control the sprayer. A global positioning system was used to locate the sprayer in the field. In both fields, Alopecurus myos-uroides was observed at low infestation levels, Galium aparine at medium infestation levels and the mean density for other broadleaf species exceeded 40 weed seedlings va- in both fields. Herbicide application was recommended for 58.3% of the first field and 54.6% of the second field. With the patch sprayer used for this study, 21% less herbicides were sprayed compared to an uniform broadcast application. Additional assessments of weed density in the first field 3 and 6 weeks after site specific weed control showed that almost the entire field was weed free. The results of this study demonstrated that site specific weed control was technically feasible but further investigations are needed to verify and evaluate site specific weed control methods. 相似文献
105.
梨树风送喷雾关键作业参数优化与试验 总被引：2，自引：1，他引：2
针对目前不同叶面积体密度果树风送喷雾关键作业参数设置缺少可操作性依据,该文通过叶面积体密度、出口风速、穿透距离对雾滴在树冠中的穿透率、沉积率及飘移率的影响试验,并以穿透率、沉积率和飘移率为评价指标,分析得出不同叶面积体密度果树喷雾的最佳出口风速。同时,根据叶单位面积所需药量标准,提出了估算喷雾机行驶速度的方法,从而优化了梨树风送喷雾的关键作业参数。该文还在试验基础上,建立了树冠内的雾量衰减模型。经检验,雾量衰减模型决定系数R2在0.90以上,平均预测误差在20%以内,有较高预测精度,能较好地预测树冠内各点雾量的分布,可对出口风速、行驶速度等参数的优化作进一步的定量分析。该文为实际喷雾作业参数的优化设置提供了参考。 相似文献
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