不同规模灌溉管网优化设计

Optimization Design of Irrigation Pipe Network under Different Scales

管网布置和管径组合是灌溉管网优化的2个主要方面,直接关系到灌溉工程的投资和运行。分析了管段流量、管道内径和管网投资随管网规模的变化情况,并以"丰"字形和"π"形布置为例,分析了管网布置形式、管径计算方法和灌水时长对管网投资的影响。结果表明:①管段流量与管网规模呈二次函数关系,管道内径与管网规模呈幂函数关系,单位面积上的基建费和年费用与管网规模呈幂函数关系,年运行费与管网规模呈二次函数关系,各项费用都随灌水时长的增加而降低;②"π"形布置适用于管网规模8 hm^2以上的情形,8 hm^2以下时2种布置形式均可。③计算管径时,为了节省基建费不宜采用经济流速法,为了节省运行费不宜采用求导法,以年费用最低为目标时,管网规模在2 hm^2以下时采用经济流速法,2～800 hm^2时采用经验公式法,800～3 200 hm^2时采用求导法。

The pipe network layout and pipe diameter selection are two main aspects of pipe network optimization, which are directly related to the investment and operation costs of the irrigation projects. The section flow, inner diameter of pipe and pipe network investments change with pipe network scale were analyzed in this paper, Influence of pipe network layout form, calculation method of pipe diameter and irrigation time to pipe network investment were analyzed too, taking the shape of "丰" and “π” as an example. The results show that:① The pipe flow rate has a quadratic function relationship with the scale of pipe network;the inner diameter and the pipe network scale are in a power function relationship;the infrastructure fee and the annual cost per unit area are in a power function relationship with the pipe network scale, and the annual operating fee has a quadratic function relationship with the pipe network scale;Full costs are reduced with the increase of the irrigation time;② The shape of “π” arrangement is suitable for the case of the pipe network scale of 8 hm^2 or more, both two arrangements can be used under 8 hm^2.③For the calculating the pipe diameter, the economic flow rate method is not recommend to save infrastructure costs;the method of derivation is not recommend to save operating costs;when the annual cost is the minimum, the economical flow rate method is recommend when the pipe network scale is below 2 hm^2, The empirical formula method is used at the pipe network scale is 2 to 800 hm^2, and the derivation method is used at the pipe network scale is 800~3 200 hm^2.