Study On Structure Optimization Of Branch Jet Pulse Tee And Hydraulic Performance Of Irrigation District

Pulse drip irrigation not only has the advantages of saving water,uniform irrigation,increasing production and strong adaptability,but also has high uniformity of irrigation and strong anti-clogging ability.Presently,there are more researches on the low frequency(0.016~0.200 Hz)pulse drip,but less on the high frequency(above2.5 Hz),especially on the hydraulic performance of branch jet pulse tee.In this paper,a more scientific and objective method is used to optimize the structure of branch jet pulse tee,which can generate 2.22~3.05 Hz pulse water flow depending on its own structure.Four irrigation districts were constructed by matching branch jet pulse tee,capillary jet pulse tee,branch and capillary ordinary T-type tees.By analyzing the hydraulic performance of each irrigation district under different branch tee inlet pressure,the optimal combination mode of branch and capillary tees in the irrigation district is determined,which has important scientific and practical value for promoting the theoretical research and application of drip irrigation technology.The main research contents and conclusions are as follows:(1)The nozzle width,potential difference,wedge distance,wedge radius and wall angle were selected as five main influencing factors,each of which had four levels.16groups of models are constructed by orthogonal design method and numerical simulation is carried out when the boundary condition is set as the inlet pressure of 100kPa.The evaluation index calculation results are standardized and the multi-factor comprehendsive scoring method is used to transform multi factors into a single index for analysis.The results show that the comprehensive score of the 11th branch jet pulse tee model is the highest after weighting,and its structural parameters are respectively:nozzle width is 15 mm,potential difference is 5.5 mm,wedge distance is 113 mm,wedge radius is 13 mm and inclination angle is 10°.(2)The test results of the branch jet pulse tee prototype after structure optimization show that the hydraulic performance of the prototype is close to the numerical simulation results when the inlet pressure is 80~120 kPa,in which the pulse frequency of the prototype is in the range of 2.22~3.05 Hz,the head amplitude is in the range of40.8~49.5 kPa,the head loss is in the range of 15.7~21.3 kPa,and one side average outlet flow is in the range of 3.592~4.036 m~3/h.(3)The hydraulic performance of four irrigation districts is studied.The results show that:the flow in?,?and?irrigation districts is pulse wave flow,the flow in?irrigation district is constant pressure flow;the uniformity of irrigation in each irrigation district is the highest when the inlet pressure of branch tee is 0.08 MPa.When the inlet pressure of branch pipe tee is between 0.06~0.12 MPa,the head loss of?irrigation community(branch and capillary pipe tees are both jet pulse tees)is the highest,the head loss along the way,the flow of emitter and irrigation district is the smallest;the uniformity of irrigation is the highest,irrigation uniformity coefficient is between 95.24%~96.03%,and the flow deviation rate is between 12.74%~18.55%.(4)The hydraulic performance of the branch capillary jet pulse tee in?irrigation district was analyzed.The results show that the amplitude,frequency and loss of water head of branch jet pulse tee are smaller than those of capillary jet pulse tee.The relationship between the hydraulic performance parameters such as the pulse characteristics(head amplitude and pulse frequency),head loss and the pressure at the inlet and outlet of the branch pipe is fitted.It is found that the relationship between the pulse characteristics vs the pressure at the inlet of the branch and capillary pipe tee is the highest fitting degree with the quadratic function,and the relationship between the head loss vs the pressure at the inlet and the average pressure at the outlet of the branch and capillary pipe is the highest fitting degree with the primary function.(5)The two fitting relations of hydraulic parameters in irrigation area are verified,that is to say,the theoretical inlet pressure of branch pipe tee in irrigation area is 0.0741MPa and 0.0803 MPa respectively when the average flow of emitter is 1.239 L/h,through the relations of outlet flow vs inlet pressure and head loss vs outlet pressure.Both results are close to the actual inlet pressure of 0.08 MPa,which shows that the fitting relationship is reliable.