Study On Hydraulic Characteristics Of Drip Irrigation System With Reversing Flow Looped Pipe Networks

On the basis of the circular arrangement of drip irrigation capillaries,this paper presents for the first time a new irrigation method of supplying water by reversing flow.Within one irrigation duration,the water supply is divided into two stages,and the water supply time of the forward flow and the reverse flow respectively accounts for half of the irrigation cycle.Then,on the basis of theoretical analysis,a hydraulic calculation program is compiled to Study the hydraulic characteristics of the pipe network of the drip irrigation system under different conditions.Get the main research results:(1)the hydraulic calculation of the loop field pipe network of drip irrigation must not only ensure the water and energy balance of the loop system,but also take into account the outflow characteristics of the emitter.ln the process of calculating the hydraulic elements of the pipe network,there are two iteration loops.One is the adjustment of the looped pipe network,the second iteration is to satisfy the pressure-flow relationship of the dripper.Based on this,the hydraulic calculation model is established and the calculation program is worked out by software.The accuracy of the program is verified by comparing the experimental data.(2)When reversing the water supply,the dripper flow is the weighted superposition of the drip flow of the forward and reverse stream,which is the weighted flow value.For the same capillary,the closer to the two side branches of the water supply,the greater the weighted flow value of the emitter,and in the middle of the capillary,the weighted flow value of the emitter is the smallest.Compared with the one-way water supply,the drip irrigation ring net can significantly reduce the flow deviation rate in the same irrigation area,but the improvement of the irrigation uniformity is limited.(3)The degree of influence of the geometric elements of the pipe network and the characteristics of the dripper on the uniformity of the irrigation and the deviation rate of the flow rate of the reverse-flow drip irrigation system is:capillary diameter>dripper spacing>capillary spacing>branch diameter.(4)under the flushing condition,because of the flushing flow in the capillary tube,the velocity of flow in the capillary tube section changes more uniformly.When the minimum flow rate of pipe section meets the requirement of flushing flow rate,the increase of capillary diameter makes the system water supply flow increase significantly,while the increase of branch pipe diameter has no obvious effect on the system water supply flow.(5)the water supply of the drip irrigation loop field pipe network in the reverse flow is compared with that in the single flow,In the same irrigation area,the rate of flow deviation can be significantly reduced,and the irrigation uniformity can be improved;The control area of drip irrigation system can be greatly increased under the condition of satisfying the requirement of flow deviation rate in the technical specification of drip irrigation.