The Optimum Design Of Tree Pipe Network For Self-Pressure Drip Irrigation System In Mountainous Areas

As a kind of precision irrigation technology,drip irrigation is very suitable for mountainous areas.Its small-flow infiltration method greatly improves the utilization of irrigation water and has obvious economic benefits.Therefore,it has been widely used in practical engineering in recent years.However,the design of the mountain drip irrigation system is different from the field drip irrigation system.There are big differences in pipe network layout,irrigation system formulation,parameter selection,hydraulic calculation and equipment selection.Therefore,there is no complete design method.And in the field pipeline installation,there are more materials and pipe fittings required,and the pipe network investment is higher.So,it is important to carry out a systematic design of the mountain drip irrigation system and optimize the pipe network.It can not only improve its design theory,but also save investment and reduce losses.This paper takes the mountain drip irrigation system in Yulin area of northern Shaanxi as the research object.On the basis of summarizing the similar conditions of drip irrigation system and its pipe network optimization at home and abroad,based on the existing deficiencies,we have designed a mountain drip irrigation system by combining theoretical knowledge with practical application,computer simulation and case verification.And then the optimal design of the pipeline network is carried out through the layout and diameter of the pipeline network.We use the genetic algorithm toolbox of MATLAB to solve the problem,and get the following conclusions:(1)The design of the mountain drip irrigation system and the design of the field drip irrigation system are similar in system composition.There are big differences in the layout of the pipe network,the selection of design parameters,and the division of the wheel irrigation area.It can be properly referenced but not completely in the system design.In mountain drip irrigation system,topography and elevation difference should be taken into account.Stereo tree-like pipe network layout should be the main form of pipe network layout.The selection of design parameters should be appropriately enlarged.The principle of near-elevation difference,near-discharge and near-location should be followed in the division of rotation irrigation areas.In addition,mountain drip irrigation system pays attention to pressure balance,so it is necessary to select high-quality,high matching degree and do a good job in equipment selection.Finally,the hydraulic analysis of the pipeline matches with a good operation and management mode to form a reasonable and applicable drip irrigation system in mountainous areas.(2)In this paper,two-level optimization methods are used to optimize the pipeline network layout.Minimum spanning tree method based on graph theory and incorporating the designer's experience is adopted to transform the pipe network connection diagram into a directed network topology diagram.In the optimization of pipe diameter,the first optimization model is established for the purpose of economy,and the second optimization model is established by adding reliability.The results show that: Model 1 has the lowest investment in pipeline network,followed by model 2 and economic flow rate method.The law of gravity head utilization rate is the same.In terms of reliability,the economic velocity method is the highest,the model one is the lowest and the model two is between.The reliability and economy of model 2 are not the best separately,but model 2 is the best choice considering both economy and reliability.In practical projects,appropriate schemes should be selected according to the needs.(3)The genetic algorithm has high efficiency,stable convergence and ideal optimization results in solving pipeline network optimization problems.Among them,the integer coding method is simple and practical,which can improve the efficiency of the algorithm and the optimization result is commercial standard diameter.The penalty function method of simulated annealing is used to deal with constraints,which improves the subjectivity of determining penalty factor and avoids the algorithm falling into local optimal solution.