Research On Structure Optimization And Application Mode Of Automatic Flushing Valve In Drip Irrigation System

Emitter clogging is a difficult problem in the promotion and application of drip irrigation technology.Regular flushing of drip irrigation system can significantly improve the anti-clogging ability of emitter and prolong the service life of drip irrigation system.The automatic flushing valve of the drip irrigation system is installed at the end of the dripline.With the help of the water flow pressure,the key structures such as the delayed channel,the water storage cavity and the elastic diaphragm can be used to realize the automatic opening and closing of the drip irrigation system during the start-up of the drip irrigation system,without external energy control,green and efficient.However,the existing automatic flushing valves have problems such as large pressure（H_a）required for automatic closing and short flushing duration（FD）.In addition,the flushing process changes the pressure and flow distribution of the drip irrigation pipe network system,and the existing drip irrigation system design method cannot meet the design and application of the automatic flushing drip irrigation system.Therefore,this paper focuses on the hydraulic performance improvement mechanism of automatic flushing valve,structural optimization and finalization,and hydraulic calculation model construction of automatic flushing drip irrigation system,so as to provide theoretical basis and technical guidance for the development and application of automatic flushing valve.The main research results are as follows:（1）Study on the response mechanism of hydraulic performance of automatic flushing valve to key structural factors.The three key structural parameters of the elastic diaphragm hardness（E）,the offset distance of the ascending channel（D）and the width of the drain hole（W）of the automatic flushing valve were taken as the test objects to explore their effects on the hydraulic performance of the automatic flushing valve.The results showed that FD and flushing water（FQ）were negatively correlated with the inlet pressure（H_a）of the flushing valve,and the flushing velocity（FV）was positively correlated with H_a.FD was negatively correlated with E and W,and positively correlated with D;FQ was negatively correlated with E,positively correlated with D,and increased first and then decreased with W;FV was mainly related to H_aand less affected by E,D and W;（2）Optimization combination and series finalization of structural parameters of automatic flushing valve.Orthogonal experimental design and hydraulic performance test method were used to explore the influence of the combination of three key structural parameters of E,D and W on the minimum closing pressure(H_amin)and maximum flushing duration(FD_max)of the flushing valve.The results showed that H_amin was positively correlated with E and D,negatively correlated with W,FD_max was negatively correlated with E and W,and increased first and then decreased with D.E,D and W had significant effects on H_amin,and E and W had significant effects on FD_max.When E,D and W are 40 HA,0 mm and 2 mm respectively,the minimum H_amin is 0.022 MPa;when E,D and W are 40 HA,2 mm and 1 mm respectively,the maximum FD_max is 116.4 s.（3）The establishment of hydraulic calculation model of automatic irrigation drip irrigation system.Based on the EPANET software and the experimental results of the automatic flushing drip irrigation system,a new module of’Emitter+TCV’for EPANET to characterize the automatic flushing valve was created,and the automatic flushing drip irrigation system model（AFDM）was constructed.The hydraulic simulation parameters of the model（flow coefficient k_a,flow index x_a,valve loss coefficient F_a）were calibrated and verified.The F_a of the three automatic flushing valves was determined to be 66.6,x_a was 0.4826,and k_a was 0.0907,0.0909and 0.0945,respectively.The normalized root mean square error（n RMSE）and the consistency index（d）were used to evaluate the accuracy of the model（n RMSE=4.9%～6.0%,d=0.9467～0.9791）.（4）Study on the application mode of automatic flushing valve in sediment water drip irrigation system.According to the AFDM model,12 scenarios were simulated after adding automatic flushing valves to the existing drip irrigation sunflower and corn projects（3specifications of automatic flushing valves:F1,F2 and F3,4 flushing valve layout modes:m=1,2,5 and 10）.The simulation results show that adding automatic flushing valves can reduce the system design pressure(H_ps)by 34.4%～46.3%and reduce the system design flow rate(Q_ps)by 68.1%～72%.In the automatic flushing of the Yellow River water drip irrigation project,the sunflower crop planting area selects the F3m5 combination to ensure the system flushing effect without replacing the current equipment in the project area.The F3m5 combination is selected in the corn crop planting area to ensure the flushing effect of the system,but the larger flow pump needs to be replaced.