【作者】 李宝珠；

【导师】 林性粹； 何林望；

【作者基本信息】 西北农林科技大学 ， 农业工程， 2008， 硕士

【摘要】 微灌,即是按作物需水要求,通过管道系统与安装在末级管道上的特制灌水器,将水和作物生长所需的养分以较小的流量均匀、准确的直接输送到作物根部附近的土壤表面或土层中的灌水方法,包括滴灌、微喷灌、涌泉灌、渗灌等,由水源工程、首部枢纽、输配水管网、灌水器4部分组成。微灌属局部灌溉,以低压(工作水头相对较低)小流量出流为主要特征,一次灌水延续时间长、灌水周期短、可精确控制水量和灌溉湿润范围,并能把水与养分直接输送到作物根部的土壤中去,节水、节地、节能效果显著,易于实现自动化控制管理。随着水资源开发利用率的提高,微灌技术应用推广面积不断增加,关于微灌工程投入主体输配水管网的优化设计理论方法层出不穷。尽管如此,还存在着诸多值得研究的问题:优化设计基于既定的管网布置,难以实现整体优化;管网布置很大程度上决定于规划设计工作者的经验;微灌工程管网布置形式单一,环状管网、树状管网和混合管网三大类管网布置形式中,树状管网是最常见的管网布置形式,特别是在微灌工程中应用广泛。基于微灌工程管网研究中存在的问题,本论文对环状管网用于微灌工程时的水力解析、优化设计及环状管网在微灌工程中应用投资低于树桩管网的条件、环状管网系统运行特性等,进行了系统研究,并通过设计实例进行了验证分析,得出主要结论如下:1.微灌工程环状灌网水力解析单环与双环单出水口微灌工程水力解析较为简单,当系统流量、管道布置等确定时,可通过数学运算计算管段流量和水头损失,求解管径。双出水口及多出水口管网水力解析复杂一些,可试算确定。2.微灌工程环状灌网设计水头优化微灌系统设计水头决定了选用管材的压力等级,和工程输配水管网投资基本成正比例关系,选用0.3MPa的管材比选用0.4MPa的管材节省25%以上的干管投资费用;微灌系统设计水头与运行电费成正比例关系;当管网投资相同或相近时,可选用管径较大、承压等级较小的管道以降低能耗。对流态指数大于0.571的微灌灌水器,降低工作水头运行在一定范围内有利于延长毛管铺设长度或提高灌水均匀度,减少轮灌组数,提高管道利用率。3.微灌工程环状管网技术经济指标对于单环管网,当管网布置长宽比LB:LA>0.8时,采用环状管网布置较为经济,较树状管网布置可节省40%以内的干管投资费用;对于双环管网,当LB:LA>1时,采用环状管网布置较为经济,较树状管网布置可节省55.5%以内的干管投资费用。输水能力相同时,采用树状管网布置比采用环状管网布置管径要大一至两级以上。环状管网管道利用率为100%,较相应的树状管网管道利用率可提高一倍以上;出水口距流量入网节点的距离最接近环长二分之一时,环网总水头损失最大;最大需要扬程(最大水头损失)相同时,环状管网较树状管网需要扬程变化范围小,即出水口间压力差较小,系统运行时水泵工况点分布相对集中,利于系统稳定运行。更多还原

【Abstract】 Micro-irrigation is a kind of irrigation method which is based on the demand of the plant , transports the water and nutrition well-distributed and accurately with little flow to the root zone through the piping system and emitters on the last pipe, including drip irrigation, micro sprinkler irrigation, bubble irrigation and seeping irrigation, etc. Micro-irrigation system is made up of water resource project, head control, transport and distribution pipe networks, emitters. Micro-irrigation belongs to partial irrigation and the small flow under low pressure is its major feature. With duration of one irrigation long , designed irrigation cycle short, controlling water quantity and wetted scope accurately, and transporting directly the water and nutrition to the root zone, micro irrigation can save water, land, energy and be easy to carry out autocontrol management.With the development and utilization rate of water resource rising and the area applying the micro irrigation technology increasing, the optimizing design theory and method emerged in endlessly. But there are some problems deserving of study. For example, the optimizing designs based on established pipe network layout are difficult to be realized overall optimization; The pipe network layout hangs chiefly on experiences of designers; The pipe network form is single, the common pipe network is tree pipe network and widely applied especially in micro irrigation project among the tree pipe network, the looped pipe network and the mixed pipe network. Because of the problems mentioned above, hydraulic analysis and optimal design and operating characteristic of looped pipe network applied in micro irrigation were researched in this paper, as well as the condition on which the invests of looped pipe network is lower than those of tree pipe network applied in micro irrigation project. And through the exemplification and analysis, the principal conclusions were obtained as follows:1. Hydraulic Analysis of Looped Pipe Network Applied in Micro-irrigation EngineeringHydraulic analysis of single outlet of single-loop or double-loop pipe network is simple, the pipe water flows and water head losses can be calculated through the mathematical calculation when the flows of system and pipe network layout established, then the pipe diameter can be calculated. Hydraulic analysis of double-outlet or multi-outlet are more complicated and can be determined by tentative calculation. 2. Optimal Water Head Design of Looped Pipe Networks in Mirco-irrigation EngineeringDesign water head of mirco-irrigation system determines pressure class of selection pipe and is basically in direct proportion to investment of water distribution networks. Selecting 0.3MPa pipe can save the investment of main pipeline of more than 25%, compared with 0.4MPa pipe; Design water head of mirco-irrigation system is direct proportion to operating electricity charges ; When investment of pipe networks is same or similar,selecting larger diameter pipe and lower pressure pearing rate can reduce energy consumption. For emission exponent of emmiter higher than 0.571, decreasing working head is favor of prolonging lateral laying length or raising irrigation uniformity,reducing Rotation Irrigation times and improving using efficiency of pipeline.3. Technical and Economic Index of Looped Pipe Networks in Mirco-irrigation EngineeringFor single-looped pipe network , when LB:LA of pipeline net layout is greater than 0.8, adopting looped pipe network layout is more economical and can save the investment of main pipeline of less than 40% ,compared with tree pipe network layout; For double-looped pipe network , when LB:LA of pipeline net layout is greater than 1, adopting looped pipe network layout is more economical and can save the investment of main pipeline of less than 55.5%,compared with tree pipe network layout;As water transportation capacity is same, Pipe Diameter 0f using tree pipe network layout can be larger one to two grade than looped pipe network layout, utilizing efficiency of looped pipe network is precent 100 and higher one than tree pipe network;When distance between water outlet to node of pipe network is close to half of cycle length ,total water head loss of looped pipe netwotk is the largest; As maximum lifting height is same(maxium water head loss) ,lift height changing range of looped pipe network is less than tree pipe net,that pressure difference between outlets is less, centralization of pump working extents in system operation is propitious to stability of system running.更多还原