Research On The Hydraulic Of Looped Pipe Networks In Micro-irrigation Laterals

Tree-type pipe networks are mostly used in our country for micro-irrigation engineering.Relative to the looped pipe networks，the pressure of tree-type pipe networks node changes alot along the pipeline，and dripper discharge is uneven，and pipeline utilization rate is lowwith some pipeline idled. So the full use of drip irrigation technology efficient water has beenaffected. Looped pipe networks has been less used in the irrigation project，although it has theadvantages of reliable water supply, relative equilibrium node pressure, high pipelineefficiency. Therefore, the hydraulic of looped pipe networks in micro-irrigation laterals，suchas The node pressure distribution and the pipe flow distribution，is analyzed to provide somereference for looped pipe networks of micro-irrigation. What’s more, the influence of lateralinlet operating pressure, lateral length, lateral diameter and dripper discharge on irrigationuniformity and the flow deviation for micro-irrigation lateral looped and tree-type pipenetworks is analyzed through an experiment. And the water conservancy parsing of simplelooped pipe networks has also been analyzed. Through the above research， the mainconclusions are as follows:(1) The flow distribution of looped pipe networks system is more uniform under differentworking pressure and the amplitude of flow distribution is smaller than that of tree-type ones.And this trend will be more obvious with the increase of work pressure. When the irrigationsystem has less ring number, the total flow of looped pipe networks branch is almost assignedto the laterals on average.(2)The irrigation uniformity of looped pipe networks increases as lateral inlet operatingpressure do. And the irrigation uniformity of looped pipe networks is higher than that oftree-type networks. Consequently, the looped pipe networks is conducive to improve theirrigation uniformity of the entire network. In addition, due to the effect of pressurecompensation in the looped pipe networks, the irrigation uniformity distribute as parabolawith the increase of ring number.(3) The each measuring point pressure values of looped pipe networks are higher thanthat of tree-type pipe networks under three working pressure. And the pressure difference oftwo pipe networks at the same measuring point become bigger as the increase of ring(tree)number. The pressure loss of looped pipe networks is small. In addition，amplitude of each measuring point pressure values of looped pipe networks is smaller than that of tree-type ones.The pressure distribution of looped pipe networks is more uniform. Therefore，the looped pipenetworks is conducive to improve the stability of the pipeline system pressure.（4）Irrigation uniformity of both looped and tree-type pipe networks increases as lateralinlet operating pressure and lateral diameter do, on the contrary, it decreases as lateral lengthand dripper discharge increase. Under the same condition, the irrigation uniformity of loopedpipe networks is1%～2%more than that of tree-type ones. Flow deviation rate of bothlooped and tree-type pipe networks decreases as lateral inlet and lateral diameter increase, onthe contrary, it increases as lateral length and dripper discharge do. Flow deviation of loopedpipe networks caused by all the four factors is basically within20%, meeting engineeringdesign requirement, while that of tree-type ones is more than20%. Consequently, looped pipenetworks can improve irrigation quality of micro-irrigation system.（5）According to variance analysis, lateral diameter has a significant influence onirrigation uniformity of looped pipe networks. For irrigation uniformity of tree-type pipenetworks, lateral diameter and dripper discharge have significant influences on it. Besides, thecorresponding F-values of looped pipe networks are smaller, so with more stable hydrauliccharacteristic, they are easier for operating and managing and are widely applied. Lateraldiameter has a significant influence on flow deviation of both looped and tree-type pipenetworks. In looped pipe networks, it doesn’t have a significant influence on flow deviationrate to lower pressure head, increase lateral length or enlarge dripper discharge. It isconsiderable to adopt looped layout in micro-irrigation engineering design.（6）The initial flow distribution of looped pipe networks in micro-irrigation lateral isdetermined on the basis of test. Though the study of looped pipe network hydrauliccalculation in micro-irrigation，the looping equation can be solved using initial flowdistribution formula Eq.(4-4) to calculate initial flow when the pipe ring number is less thanfive. for single looped pipe networks in micro-irrigation lateral，when the system flow andthe pipeline arrangement is known，the pipe flow and node pressure can be calculated usingEq.(4-7) to Eq.(4-15). For the hydraulic analysis of double looped pipe networks inmicro-irrigation lateral，the pipe flow and node pressure can be calculated using Eq.(4-16)to Eq.(4-23). For the complex pipe network with more rings，it can be calculated with thehelp of a computer program for further analysis.