滴灌加压泵站运行工况的设计依据研究

To the pressure pumping station which services a sizeable drip irrigational system, the head loss of pipe network system would be changed of the spatial variation of rotation irrigational set, therefore the operating conditions of the pumping station would be variable always; in addition, the operation conditions of filter system are also variable with operating time, so the operation conditions of the pumping station and the pipe network system are fluctuated. This performance of drip irrigation system induces difficult design to the operation conditions of pressure pumping station under the dearth of technical bases or standards now. In view of this problem, the technical bases for designing the operating conditions of the pressure pumping station for drip irrigation system are studied in this project. It would be studied that (1) the response of drip irrigation system characteristic curve to the spatial change of water use point and multivariate form of the pipe network system; (2) the interference effect of filter system operating conditions in the pipe network operation of drip irrigation system; (3) the control models of pressure pumping station operating for drip irrigation system. In the study, various forms of pipe network system would be planned as well as the rotation irrigation combination to calculate the head change of the pipe network, and to erect the functional of drip irrigation system characteristic curve, then correct the functional by experimental data. By observing the interference effect of the filter system operating in the pipe network operation, the control model consist of pump characteristic curve, drip irrigation system characteristic curve, and the filter system operation curve, would be formed with the modern control theories. Finally, the technical bases for designing the operating conditions of pressure pumping station are obtained by dynamic simulating based on the control model.

对于控制面积较大的滴灌加压泵站，轮灌组空间位置变化将造成管网水头损失的变化，使得泵站运行工况始终处在变动之中；加之过滤系统运行工况的随时变化，更引起泵站和管网工况的波动。滴灌系统的这一运行特征导致加压泵站的工况设计较为困难，而目前尚没有关于设计滴灌加压泵站运行工况的依据。鉴于此，本项目针对“滴灌加压泵站运行工况的设计依据”问题，研究（1）滴灌系统装置特性曲线对管网多元结构及用水点空间变化的响应；（2）过滤系统运行工况对滴灌管网运行工况的干扰效应；（3）滴灌加压泵站运行工况的控制模型，等3个内容。研究中，通过设计不同管网布置形式和轮灌组合推算管网水力变化，构建装置特性曲线的泛函数，并进行实验修正；观测过滤系统工况对管网工况的干扰形式，利用现代控制理论建立由水泵特性曲线、装置特性曲线和过滤工况曲线组成的控制模型；通过动态模拟得到泵站运行工况设计依据。

滴灌泵站设计中以最不利工况作为选泵原则，不考虑滴灌系统工况变化引起的田间各轮灌组之间的供水不均衡现象，这是导致生产实践中部分轮灌组低压运行、滴灌均匀度降低的原因之一。本项目通过田间观测和理论分析探明引起滴灌泵站工况变化的原因和对工况的影响程度，提出合理的选泵依据。田间观测结果证实，滴灌轮灌组在田间运动时引起泵站装置特性曲线变化，进而引起泵站扬程变化；当泵站控制面积为2000亩时，泵站扬程变化幅度为4~6 mH2O；如果泵站选用Q-H曲线缓降型水泵工作，由此引起的流量差异达到47~201 m3/h；泵站控制面积越大，各轮灌组之间的流量差异也就越大。田间观测结果还表明，泵站过滤系统的工况变化对泵站工况也有显著影响，而且过滤系统的工况变化规律比较复杂，其不仅受水质的季节性变化影响，还受水肥一体化灌溉要求的影响。初步的理论分析结果建议，滴灌泵站设计中选择Q-H曲线陡降型水泵工作更合理；田间滴灌系统以“丰”字形布置，更有利于减小滴灌施肥对轮灌组工况的影响。项目研究中受到“新冠”疫情的严重影响，使得部分研究工作没能完成。