【作者】 朱兴业；

【导师】 袁寿其； 李红； 汤跃；

【作者基本信息】 江苏大学 ， 流体机械及工程， 2009， 博士

【摘要】 全射流喷头是我国具有自主知识产权的一种新型节水灌溉产品,应用水流附壁效应完成直射、步进和反向的功能,具有结构简单、造价低、无撞击部件、能量损失小和喷洒性能好等优点。对于此类新型产品,研究尚不够深入,对其进行系统研究具有很高的学术价值与实用意义。本文介绍了全射流喷头的原理和特点,通过理论分析、试验研究和数值模拟相结合的方法,对全射流喷头理论及精确喷灌关键技术进行了系统研究。主要研究工作和创新点有:(1)通过54次的正交试验,初步提出了全射流喷头设计方法。采用四因素三水平的正交试验获得了喷头主要结构参数影响关系:影响步进频率主次顺序为收缩角、取水孔角度、位差和作用区;影响步进角度主次顺序为位差、收缩角、取水孔角度和作用区。喷头重要结构参数中,基圆孔大小由喷头型号决定,补气孔和入水孔设计方法相同,收缩角选取14°,取水孔角度选取30°,用二次曲线方程回归分析得出位差与喷头基圆孔函数关系式,以及作用区与喷头基圆孔函数关系式。(2)首次研制开发了新型连续运转射流喷头、外取水射流喷头、三段式射流喷头和两次附壁射流喷头,分别介绍了它们的结构和工作原理。采用五因素四水平表对连续运转射流喷头和四因素三水平表对外取水射流喷头进行了正交试验研究,获得了连续运转射流喷头和外取水射流喷头的最优结构参数,开发了国内原创的喷灌设备。(3)总结得出全射流喷头力学特性的计算公式,通过试验与摇臂式喷头工作性能的对比,结果表明全射流喷头步进角度和步进频率可调幅度较大,均优于摇臂式喷头。为了扩大全射流喷头压力适用范围,提出在喷管处加转折角以增加喷头固有驱动力矩。转折角喷管的重要结构因素包括转折角角度和转折角力臂长度,选用7种不同的转折角角度或转折角力臂喷管进行试验,测量步进角度、步进频率、射程和均匀系数等性能指标。结果表明:转折角角度增大,步进角度增大,均匀系数增大,步进频率减小,射程变化不大;转折角力臂加长,步进角度增大,射程减小,步进频率和均匀系数变化不大。(4)建立了全射流喷头内部流场的CFD数学模型,采用FLUENT软件对喷头内部流场进行了数值模拟。在转折角喷管角度为2°和5°时,通过数值计算喷管推动力、转运驱动力和流量之间的关系,理论计算结果与CFD数值计算结果平均偏差小于5%。对喷头的流量—内部压力关系,喷头附壁点的位置,不同插拔深度、管长或工作压力情况下的喷头步进频率进行了较详细的数值计算,与试验结果进行对比,表明两者具有较好的一致性,说明采用CFD方法能较好地反映喷头的内部流动情况。(5)对全射流喷头实现变量喷洒进行了理论研究,推导出喷头实现正方形喷洒的边界方程,采用MATLAB语言对射程、工作压力与运行时间进行仿真。设计出实现正方形喷洒的全射流喷头动静片结构,经过外特性试验测量喷洒水量分布,绘制出三维水量分布图。将变频调速技术引入喷灌系统,对变域喷洒系统进行能耗分析,利用虚拟仪器技术测量采集试验数据。试验表明:机械方式设计动静片和利用变频调速都可以实现正方形的变量喷洒,为今后进一步开展变域喷洒喷头研究提供了理论基础。(6)对全射流喷头组合喷灌进行研究,分析处理喷头水量分布数据、实现三维可视化。研究表明:MATLAB语言可方便可靠地将喷头径向水量分布数据转换为网格型数据,并绘制出单喷头和喷头组合三维水量分布图。通过插值叠加求出各网格点总降水深,求出不同组合间距系数下的全射流喷头组合均匀系数,实现计算结果可视化。根据模拟分析,提出正方形布置时组合间距系数为1.2,各喷头均匀系数平均值为82.4%。三角形布置时组合间距系数为1.5,各喷头均匀系数平均值为85.7%。运用MATLAB语言编程进行喷头喷洒分析具有功能强大、方便快捷、可视性强等优点,适用于任何喷头水量分布的分析。(7)针对产业化生产出的系列PXH型塑料全射流喷头,通过田间试验提出了6个方面的改进措施,主要为修改空心轴与连接套配合尺寸和两片四氟圈之间的相互配合,以增加喷头田间运转可靠性。改进后可望进行大批量产业化生产。更多还原

【Abstract】 This project was supported by the National High-tech Research and Development Program (Grant No. 2006AA100211)—"Light-duty Irrigation System for Variable Sprinkling".The complete fluidic sprinkler, a new type of water-saving product, which depends on the theory of Coanda effect to accomplish the function of direct-spraying, stepping and reversing, was originally invented in China. We have had the intellectual property and have owned several correlative patents. The sprinkler has several advantages, such as easy-constructed, low loss of energy, low price and so on. For such new products, research was not deep enough now. Systematic research for the complete fluidic sprinkler has high academic value and practical significance. First, the working principle and characteristics were introduced. Combined with theoretical analyses, experimental tests and numerical simulation, the theory of the complete fluidic sprinkler and the technology of the precise sprinkling irrigation were systematically investigated. The main contents and innovations in this dissertation were as follow:1. After fifty-four tests, design method of the complete fluidic sprinkler was put forward firstly. An orthogonal array with four factors and three levels was selected to carry out the experiments. The relationships between the main sprinkler structure parameters were obtained: the influencing factors in decreasing order of importance for stepped frequency are contractive angle, water fetching angle, offset length and working area; the influencing factors for stepped angle are offset length, contractive angle, water fetching angle and working area in decreasing order of importance. The important structure parameters were confirmed as follow, the size of base circle is determined by the type of the sprinkler. Design method for water inlet and air inlet were the same. 14 and 30 degrees were defined for contractive angle and water fetching angle respectively. The equation of offset length and base circle relationship as well as the equation of working area and base circle were established using the method of quadratic regression analysis.2. Some kinds of new type of fluidic sprinklers were developed, including the continuous operated fluidic sprinkler, the outside signal fluidic sprinkler, the three section fluidic sprinkler and the twice wall-attachment fluidic sprinkler. Their structure and working principle were described respectively. An orthogonal array with five factors and four levels was selected to carry out the experiments for the continuous operated fluidic sprinkler. An orthogonal array with four factors and there levels was selected to carry out the experiments for the outside signal fluidic sprinkler. The best values of their structure parameters were confirmed after the experiments.3. The formula for calculating the mechanics characteristics of the complete fluidic sprinkler was summarized up. The performance parameters for the complete fluidic sprinkler and impact sprinkler were contrasted by experiments. The results demonstrated that the adjustable range of stepping angle and frequency for the complete fluidic sprinkler was much bigger than that of the impact sprinkler. To enlarge the scope of working pressure for the complete fluidic sprinkler, the turning angle was added in the effuser. It can increase the intrinsic driving moment for the sprinkler. The important structure parameters for the turning angle effuser included the angle and arm of force. Experiments were carried out based on seven effusers of different turning angles or arms of force. It can be seen from the results that the testing value agreed well with the theoretical analysis. Turning angle positively influenced the stepping angle and uniformity coefficient, while negatively influenced the stepping frequency. Turning arm of force positively influenced the stepping angle, and negatively influenced the wetted diameter.4. Mathematical model for the inner flow of the complete fluidic sprinkler was established using computational fluid dynamics. The FLUENT was used to numerical simulate the inner flow of the sprinkler. When turning angle was 2 or 5 degree for the effuser, the relationships between driving force, transfer driving force and flux were calculated by numerical simulation. The average deviation of the results between theoretical analysis and numerical simulation was less than 5 percent. Computational fluid dynamics method was applied to calculate the stepping frequency, the lean-wall position and the relationship between flux and working pressure. The simulated results agreed well with the experimental results.5. The theoretical study of variable irrigation for the complete fluidic sprinkler was carried out. The boundary equations of rectangular irrigated area were developed. The relationships between wetted diameter, working pressure and operated time were simulated using the MATLAB programe. The activity pieces to achieve rectangular irrigation for the complete fluidic sprinkler were designed. The irrigated water distribution was measured and the three-dimensional water distribution picture was drawn. The frequency control technology was brought into the sprinkler irrigation system. Energy consumption analysis was carried out for the variable-rate irrigated system. The data was tested and collected using the virtual instrument technology. The results demonstrated that rectangular irrigation can be achieved both by mechanical activity pieces designing and frequency control technology. It supplied theoretical foundation of variable rate irrigated sprinkler for the future. 6. Combination irrigation for the complete fluidic sprinkler was studied firstly. The MATLAB was used to analyze the data of water distribution. The data can be made visible in multidimensional orientation as a result. It was proved to change the radial data into net data conveniently and reliably. And three-dimensional water distribution pictures for sprinkler and combined sprinklers were drawn. According to the tested data, the total water depth of net point was calculated using superposition method. Then the combined uniformity coefficient of the complete fluidic sprinkler was simulated in different combined spacing. After the simulation, combined spacing coefficient was chosen by 1.2 in the rectangular combination, and 1.5 in the triangular combination. The average uniformity coefficient can be 82.4% and 85.7% respectively. A case study shows that the MATLAB is reliable for simulating water distribution in sprinkler irrigation.7. Series of PXH sprinklers were manufactured into plastic sprinklers, but there were still some problems. After field experiments, six respects were put forward to improve the working conditions. There were two important respects that must be improved. First, the match of hollow shaft and connected case must be revised. Second, the two fluorine circle should be movable fitted. After the resolved schemes, the reliability of field operation was increased and the PXH complete fluidic sprinklers could be put into mass production.更多还原