微灌田间管网布置与管径同步优化及影响因素分析

田间管网是微灌系统的最基本设计单元,该部分规划设计的合理性直接影响到整个微灌系统的工程投资及运行费用。将田间管网作为一个整体,分别以单位面积年费用最低及控制面积最大为目标,在不限定田间管网形状及面积的情况下建立毛管单向布置及双向布置田间管网优化设计数学模型。分析了毛管管径、灌水器设计流量、灌水器间距、毛管方向地面坡度、灌水器制造偏差系数及流态指数对田间管网优化结果的影响,并对两种布置模式下田间管网的优化结果进行了对比。实例计算结果表明:较小的毛管管径、灌水器设计流量、灌水器制造偏差系数及流态指数、较大的灌水器间距有利于减小田间管网单位面积年费用,减小的百分比为0.55%～57.42%;较大的毛管管径及灌水器间距、较小的灌水器设计流量、灌水器制造偏差系数及流态指数有利于增大田间管网控制面积,增大的百分比为18.31%～925.94%;毛管双向布置田间管网在单位面积年费用及控制面积两方面均优于毛管单向布置田间管网,毛管双向布置田间管网单位面积年费用较毛管单向布置降低0.59%～9.58%,控制面积较毛管单向布置增大9.67%～186.57%。结果可为不限定面积情况下微灌田间管网的优化设计提供依据。

Simultaneous optimization of micro-irrigation subunit layout and pipe diameter and analysis of influencing factors

The micro-irrigation subunit is the most basic design unit of the micro-irrigation system, its planning and design rationality directly affects the project investment and operation cost. In this study,the micro-irrigation subunit was addressed as a whole,taking the minimum annual cost per unit area and maximum control area as the objective function,the mathematical models of optimization design for subunit with unidirectional laterals and paired laterals were established under the condition of unlimited area. The effects of lateral diameter, emitter design discharge, emitter spacing, emitter coefficient of manufacturing variation,emission exponent and ground slope in the lateral direction on the optimization results of micro-irrigation subunit were analyzed,and the optimization results of micro-irrigation subunit under two layout models were compared. The example results showed that smaller lateral diameter,emitter design discharge,emitter coefficient of manufacturing variation and emission exponent,and larger emitter spacing are beneficial to reduce the annual cost per unit area of micro-irrigation subunit, the reduction ration is 0.55%~57.42%. Larger lateral diameter and emitter spacing and smaller emitter design discharge,emitter coefficient of manufacturing variation and emission exponent are beneficial to increase the subunit control area, the increase rate is 18.31%~925.94%. The subunit with paired laterals is better than the subunit with unidirectional laterals in both annual cost per unit area and control area. The annual cost per unit area of subunit with paired laterals is 0.59%~9.58% lower than the subunit with unidirectional laterals,and the subunit control area is 9.67%~186.57% higher than the subunit with unidirectional laterals. The results can provide the basis for the optimization design of micro-irrigation subunit without limiting the area.