【作者】 李云开；

【导师】 杨培岭； 任树梅； 李光永；

【作者基本信息】 中国农业大学 ， 农业水土工程， 2005， 博士

【摘要】 滴头是滴灌系统最关键的部件之一,我国设计主要是以引进和仿制为主,国内还没有一种具有自主知识产权而水力性能和抗堵塞性能俱佳的滴头,究其原因主要是缺乏流道设计理论指导。本文就是利用分形几何理论构造滴头流道,并将数字式粒子图像测速技术（DPIV）、平面激光诱导技术（PLIF）、计算流体动力学（CFD）理论应用于流道研发中,形成了滴头分形流道设计理论和平台,主要的研究内容与成果包括: 建立了基于CAD-CFD联合运用、滴头平面模型的滴头分形流道技术开发平台,提出了基于AutoCAD技术和读数显微镜联合应用的滴头流道几何参数测试方法。 基于分形几何构造复杂分形体的能力以及紊流本质的分形特征,创造性地利用Koch、Minkowski曲线为中心线或边界线构建了能够满足滴头制造的分形流道,实现了滴头流道的全紊流设计。经通径分析发现分形流道流量系数主要与流道横截面面积、流道长度有关;流道几何参数对流态指数影响微小,可以忽略不计,流态指数主要与流道结构形式有关。经量纲分析和圆管紊流理论分析表明流道内部流动的雷诺数R_e对流道摩阻系数λ影响很小,可以忽略不计;λ随R^D_f/L_n的增加而线性增加,对于滴头流道这种连续扰动引起的水头损失符合线性叠加规律。 探索性的利用显微镜物镜改装CCD相机构建了滴头流道流场的DPIV测试系统,并合作研发了DPIV示踪的荧光粒子,实现了DPIV技术与PLIF技术的结合,成功解决了流道内流动PIV测试中的图像分辨率与拍摄区域间的矛盾问题以及图像噪声干扰,国内外首次在滴头流道流动研究中实现了全场无扰测试。测试结果表明:在1.0-15.0m压力范围内分形流道与迷宫式流道内部流动为紊流,并未呈现出流态转捩行为,其主要是由于滴头流道边界复杂,更有利于水流从层流向紊流的转变;两种分形流道都存在一定的流动滞止区。 借助所构建的DPIV系统以及CFD方法对迷宫式流道内部断面平均流速以及高速区与二次流动区的大小和分布等进行研究,表明CFD数值模拟方法在滴头流道这种临界尺度流体流动研究中是适用的,并能够较为准确的预报滴头的流量-压力关系。 CFD数值模拟结果表明分形流道的紊流强度比迷宫流道的紊流强度要高,构建分形流道是同时提高水力性能和抗堵塞性能的有效途径之一。借助CFD数值试验研究提出了基于流道内部流速分布的常规滴灌和微重力滴灌用滴头分形流道优化设计方法,并建立了面向不同流量需求的滴头分形流道成型设计模式。更多还原

【Abstract】 The emitter is one of the crucial devices in a drip irrigation system which is used to dissipate pressure and to discharge water at a constant rate by dissipating energy when the pressured water flows through its internal narrow and long path structure or micro-orifice. In some foreign countries, such as in Israel, there have been mature design theories) production workmanship, and adequate application experience. Now the design of emitters in China is only in its preliminary stage of introduction and imitation. Up to now, there has been no domestic trickle irrigation emitter with self-owned intellectual property right that possesses both good anti-blocking property and good hydraulic performances. The main reason behind this situation is lack of the guidance by flow path design theories, which is not beneficial for serialization of emitters. Some famous international companies, have their own design institutes of trickle irrigation emitters. But the theories and methods for designing flow paths have been strictly confidential and the research papers on flow path of emitters with the function of practical guidance have seldom been published. In this dissertation, Fractal theory, Digital Particle Image Velocimetry (DPIV), Planar Laser-induced Fluorescence (PLIF), Computational Fluid Dynamics (CFD), and hydraulics performance experiments were combined to design new flow path of emitters.With high-speed development of modern cyber-technology, synthesizing the CAD (Computer Aided Design) and CFD has been the development trend for designing hydro-machines. By thoroughly analyzing the process of emitters design, the platform for designing drip irrigation fractal flow path emitter was formed with CAD/CFD software cooperation technologies and plane model. It was explored to measure the geometric parameters of the flow path by means of combining high-precision microscope and AutoCAD technology, and the two-dimensional model was constructed via the technology of line incision with electric spark.In this study, fractal flow path was designed with Koch and Minkowski curves to shape the boundary, and the full-turbulence design of flow path was realized. The results of path analysis showed that the cross-sectional area and length of the flow path were the primary factors affecting the flux coefficient of drip irrigation emitter. The exponent of emitter was independent with respect to parameters of the flow path, and main with respect to the structural form of the flow path. The results of dimension analysis and turbulent pipe flow theory showed that the Reynolds number Re had low effect on the flow path friction coefficientλ, which could be ignored. Friction coefficientλ was linearly increasing with augmenting of Ra /Ln , and the pressure loss was descending with linearity rules along the flow path, and the head losses due to continuous dentiform cell was equaled.It is creative that the Digital Particle Image Velocimetry sytem was conformed based on changing the CCD camera lens with microscope object lens, and the fluorescent particle was excogitated in this study. The problems of the inconsistency between digital image resolution andareas and the image noises were settled successfully. The non-intrusive and whole-field velocity measurement for velocity within the drip irrigation emitter flow path was realized in the world. The result showed that the flow regime was turbulent in labyrinth and fractal flow path under pressure Of 1.0-15.0m. The complex boundaries and curved structure within labyrinth paths of emitters facilitated the transformation of the flow from laminar flow into turbulent flow. The critical Reynolds number within the small labyrinth paths of emitters was smaller than that within the normal dimension paths. And there were some stagnant areas (including the low velocity areas) in the fractal flow path.The average velocity magnitude, distributing vorticity magnitude, magnitude and distributing of high speed areas and second flow ones, and the turbulence intensity distribution within the three typical column labyrin更多还原