| Pulsed drip irrigation is an irrigation technology with strong anti-clogging performance and high irrigation uniformity.It is widely concerned and applied by various countries in the world.The existing pulsed drip irrigation generally uses electromagnetic pulse devices,pulsed electromagnetic valves or rubber,springs,to form pulsed water flow,which has a high manufacturing cost and is inconvenient to use and maintain,which limits the popularization and use of pulsed drip irrigation.In this paper,a branch tube Jet-pulse tee with simple structure,was designed based on the jet-attachment and switching principle,which spend low cost,and have high irrigation uniformity.The basic structure size was determined,and internal flow field of branch tube Jet-pulse tee was analyzed.Combining lateral pipe Jet-pulse tee studied by previous researchers and currently developed branch tube Jet-pulse tee,constructed pulsed drip irrigation district,compared with normal drip irrigation district for hydraulic performance comparison,and impulse performance of pulsed drip irrigation district was analyzed.The main works and conclusions are as follows:(1)Designed and developed a branch tube Jet-pulse tee to determine its basic structure,are respectively: nozzle width is 15 mm,sidewall angle is 10°,position difference is 5.5mm,pitch distance is 113 mm,shunt radius is 13 mm,the control tube length is 340 mm,the control tube width is 9mm,and the outlet flow path width is18 mm.The flow process of the internal flow field of branch tube Jet-pulse tee was analyzed,and the change process of the main jet flow in the flow channel,the energy transfer process of the control channel and the pressure in the low pressure vortex zone was revealed.A method for designing a branch tube Jet-pulse tee is proposed,draw a conclusion: when the boundary conditions at the outlet are constant,the position difference is too large or too small and the pitch distance is too large.The Jet-pulse tee cannot generate pulsed water flow;when Jet-pulse tee size is determined,the inlet head is too small and the outlet pipe flow formula flow coefficient is too large or too small,and the Jet-pulse tee cannot generate pulsed water flow.(2)Tested four kinds of irrigation districts,are respectively: I irrigation district(branch tube and lateral pipe are Jet-pulse tee)?? irrigation district(branch tube are Jet-pulse tee,lateral pipe is normal tee)?? irrigation district(branch tube are normal tee,lateral pipe is Jet-pulse tee)?? irrigation district(branch tube and lateral pipe are normal tee).The results found: when the inlet pressure of the irrigation area and the laying length of the capillary are same,the average flow rate at the monitoring point of I irrigation district is the smallest,and the average flow rate at the monitoring point of the IV irrigation district is the maximum;when the pressure condition is fixed,the length of the capillary tube increases,and the inlet flow rate of the irrigation district also increases;when the length of the capillary tube is same,the inlet flow rate of the irrigation area increases as the pressure increases.In the four types of irrigation districts,when the inlet pressure and capillary length are the same,the irrigation uniformity of I irrigation district is the best,and the irrigation uniformity of IV irrigation district is the worst,II and III irrigation districts are in the middle.The average value of the irrigation uniformity coefficient in I irrigation district was2.56-3.32 percentage points higher than that in IV irrigation district,and the flow deviation rate was reduced by 5.06-8.20 percentage points.(3)IV irrigation district is a pulsed drip irrigation district,and its pulse characteristics are analyzed.Draw conclusions: when the inlet pressure of irrigation district is 9.5-15.5m,the lateral pipe Jet-pulse tee head loss is between 0.6-1.9m,the head amplitude is between 1.5-6.1 m,the pulse frequency is between 200-235 times /min;branch tube Jet-pulse tee head loss is between 0.7-2.0m,the head amplitude is between 2.0-3.8 m,the pulse frequency is between 110-140 times / min.The lateral pipe Jet-pulse tee head amplitude is greater than branch tube Jet-pulse tee,and the lateral pipe Jet-pulse tee pulse frequency is greater than branch tube Jet-pulse tee.(4)Fitting the relationship between head amplitude and head loss,pulse frequency and head loss,the maximum and average inlet head respectively of lateral pipe Jet-pulse tee and branch tube Jet-pulse tee,a hydraulic design method for pulsed drip irrigation districts was proposed. |
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