【作者】 丛佩娟；

【导师】 黄修桥； 仵峰；

【作者基本信息】 中国农业科学院 ， 农业水土工程， 2004， 硕士

【摘要】 高效节水的地下滴灌技术，日益受到国内外的重视，但有关地下滴灌管道、管网的理论还不完善，系统的设计和运行管理多参照地表滴灌进行。本文针对地下滴灌条件下管道和管网的水力特性，采用试验和数学模型相结合的方法，系统地分析了地下滴灌条件下薄壁滴灌带受压变形后的水力特性变化以及对水力设计的影响，研究地下滴灌条件下各种形式管网之间的水力关系，为地下滴灌系统的设计及运行管理提供理论依据。 通过对薄壁滴灌带压缩试验和对树状、环状管网的水力特性的研究，得到以下结论： 1、地下滴灌条件下薄壁滴灌带的压缩 对于埋藏于地下的薄壁滴灌带，土壤压实会造成滴灌带横截面变形。同种压力下，滴灌带压缩程度越大，滴头平均流量减少的越多；同种压缩度(压缩量／未压缩滴灌带直径)下，滴灌带入口压力越大，滴头流量减少的越多。压缩度在50％以下的轻度变形时，对入口流量影响较小。滴灌带横截面的变形影响毛管的水力设计长度，预先估计滴灌带压缩程度，修正系数α和流量指数m的值，根据水力计算适当减小毛管设计长度，另外根据滴头平均流量的减少适当延长灌溉时间。 2、管网中支管压力分布 试验中三种管网(树状管网、单冲洗管管网、双冲洗管管网)中支管压力分布均相同，随首部压力增大而增大，压力曲线呈指数分布；采用补偿式滴头的管网压力分布略有不同，其中树状管网中支管压力达到一定数值后不再随首部压力增大而增大，而是稳定在一定数值范围内，而两种环状管网中支管压力没有体现出压力稳定情况；所有管网中支管入口压力-流量关系均可用多项式表示。 3、树状管网和环状管网毛管水力性能的关系 非补偿式管网中，相同首部压力下各毛管入口压力环状管网要略高于树状管网；三种管网毛管入口流量变化趋势一致，差异较小，变幅约为7％；环状管网滴头流量均匀性好于树状管网，在工作压力为低压时尤为明显。补偿式管网中，相同首部压力下各毛管入口压力环状管网明显低于树状管网；三种管网毛管入口流量变化趋势近似于压力变化，环状管网均低于树状管网，随着首部压力升高，三种管网流量相近，树状管网体现出压力补偿的作用，在测试压力范围内，环状管网压力补偿作用不明显。可见，在相同首部压力下，环状管网压力补偿作用滞后于树状管网；对毛管入口流量变化率分析，管网中毛管入口流量均匀性环状管网好于树状管网。 4、地下滴灌管网优化 根据地下滴灌环状管网的水力特性，建立地下滴灌管网优化计算模型，采用节点水压法对模型进行计算。与实测结果对比，模型有效可行。运用模型，对地下滴灌条件下环状管网的优化设计进行模拟计算，修正毛管设计长度，可供参考。更多还原

【Abstract】 Subsurface drip irrigation (SDI).which has more effective in water-saving, has been paid more attention by researchers all over the world. But the study on the hydraulic of pipe networks in SDI is still faultiness. Field experiments and mathematical model combined to analyze hydraulic effects of compression deformation of subsurface drip-tapes. And the hydraulic relations among kinds of pipeline networks were studied in this paper. The experimental and analytical results indicated:1. Hydraulic considerations for compressed subsurface drip-tapeReduction in average emitter flow rate corresponds to the degree of drip-tape deformation, resulting from soil compaction, and to the inlet flow rate. The effects of less 50% compression on inlet flow are less critical. The recommended maximum lateral length should be reduced based on corrected coefficient a, in ,and times of irrigation lengthened, according to the degree of anticipated compression of the drip-tape.2. Pressure distributing in the submainPressure distributing in the submain of such three pipe networks, branched networks, single flushline looped networks and double flushline looped networks are the same. Increase in pressure in the submain corresponds to the increase in the main. The pressure curve is exponential. In the pipe networks which used compensated emitters, as pressure increasing in the main, the pressure in the branched networks tends to a jarless range. Whereas the pressure in the other two looped networks differ from it. The equation relations between inlet flow and pressure in the submain of all the pipe networks are multinomial.3. Hydraulic relations between the looped networks and the branched networksIn the pipe networks which used noncompensated emitters, the inlet pressure in capillaries in the looped networks are higher than those in the branched networks. The inlet flow in capillaries in the three pipe networks are approximately identical, the diversifications of flux are in 7%. About uniformity, emitter’s discharge in the looped networks are better than those in the branched networks. And it is obviously under the low work pressure. In the pipe networks which used compensated emitters, the inlet pressure in capillaries in the looped networks are lower than those in the branched networks. The inlet flow distributing in capillaries in the three pipe networks are similar to the pressure. In the tested pressures, the branched networks showed the pressure compensate function, whereas the function of the looped networks is lagged behind the branched. The uniformity on the capillaries inlet flow, the looped networks are better than the branched.4. The optimal design of pipe networks in SDIBased on above experiments, a method of the numerical simulation for optimal designing pipe networks in SDI is presented. And it is solved with node hydraulic pressure procedure. Results showed that it is viable and feasible. With the model combing corrected coefficient a, m,the optimal design of looped networks in SDI was simulated, and to provide a reference for designing and running a SDI system.更多还原