| Sprinkler irrigation technique is an efficient and water-saving irrigation method,and the sprinkler head is a key part of the sprinkler irrigation system.The jet pulse sprinkler is a new type of rotary nozzle that realizes full-circle spraying based on the principle of jet-coated wall switching.It has the advantages of simple structure and good hydraulic performance.In this thesis,in order to increase the types and series of jet pulse nozzles,a jet pulse nozzle with an inlet diameter of 20mm is designed,and its flow channel structure is optimized,and its rotary drive structure is improved,so as to provide a reference for the follow-up research of jet pulse nozzle.The specific research contents are as follows:(1)Through the load feedback jet pulse technology,combined with the relationship between the inlet width of the jet element and the flow velocity,and considering the dynamic change of the ratio between the structural parameters,the structure of the jet element area of the jet pulse nozzle is determined.A five-factor and four-level orthogonal test is designed,and sixteen numerical simulations were carried out.Taking the pulse effect and inlet flow as the evaluation criteria,it is determined when the inlet width is 6 mm,the position difference ratio is 0.375～0.450,the split distance ratio is 5～8,the inclination angle of the side wall is 9°～12°,the outlet width ratio of the jet element is 1.2～1.8.The pulse effect of the jet element area is the best and the inlet flow rate is the smallest.Therefore,the optimization of the overall structural parameters of the jet pulse nozzle should be based on this value range is carried out.(2)Adding the factors of elbow curvature radius ratio,nozzle diameter,relative length of main and auxiliary nozzles,and diameter of main and auxiliary nozzles,two sets of orthogonal experiments were designed,and the overall structural parameters of the nozzle were optimized through 50 numerical simulations.Taking the inlet flow rate,outlet flow velocity and pressure amplitude as the evaluation indicators,the comprehensive scoring method and the range analysis method were used to analyze the test results.After the optimization of the orthogonal test,the optimal flow channel structure parameters of the nozzle are obtained as follows:the head difference ratio is 0.475,the split distance ratio is 10,the sidewall inclination angle is 11°,the outlet width ratio of the jet element is 2,the curvature radius ratio of the elbow is 9,and the nozzle diameter is 8 mm.,the relative length of the main and auxiliary nozzles is 7×7,and the diameter of the main and auxiliary nozzles is 5 mm×5 mm.For the optimal flow channel structure parameters,the numerical simulation of the nozzle under four pressures of 0.20 MPa,0.25 MPa,0.30 MPa and 0.35 MPa shows that pressure amplitude is 0.036 MPa～0.068 MPa,and the inlet flow rate is 2.431 m~3/h～3.216 m~3/h,all of which meet the test requirements.(3)After analyzing the rotational driving principle of the nozzle,four kinds of inner driving nozzle structures of arc type,straight plate type,semi-conical type and pyramid type and a sealed rotating mechanism with less friction are designed.The hydraulic performance test of four kinds of internally driven nozzles under four pressures of 0.20 MPa～0.35 MPa is carried out.The test results were the range is 15.2 m～17.1 m,the inlet flow rate is 2.172 m~3/h～3.190 m~3/h,and the sprinkler intensity is 2.969 mm/h.～3.543 mm/h,irrigation uniformity of 60.1%～85.4%,comprehensive comparison of various hydraulic performance indicators,it is finally clear the performance of the pyramid nozzle is the best.Therefore,a total of nine groups of orthogonal tests with three factors and three levels were designed to optimize the structure of the pyramid-shaped inner drive nozzle,and the range analysis method is used to analyze the test results.The excellent pyramid-shaped nozzle structure is 4.7 mm in length,8 mm in thickness,and 120°in width.(4)Carry out a comparative test of hydraulic performance between the optimal structure jet jet sprinkler and the rocker type sprinkler with the same parameters under the same conditions.The test results are:the range of the jet pulse sprinkler is 0.6%～0.6%larger than that of the rocker type sprinkler under the pressure of 0.20 MPa～0.25 MPa.0.7%,the irrigation uniformity is 1.04%～1.49%higher than that of the rocker type sprinkler,the range is 1.5%～1.7%lower than that of the rocker type sprinkler under the pressure of 0.30 MPa～0.35 MPa,and the sprinkler uniformity is 0.96%～2.76%lower than that of the rocker type sprinkler.%.However,under the pressure of0.20 MPa～0.35 MPa,the inlet flow of the jet pulse sprinkler is reduced by 14.0%to 19.3%and the sprinkler intensity is reduced by 11.6%to 15%compared with the rocker type sprinkler.The comprehensive analysis shows that inlet flow and irrigation intensity of the jet pulse sprinkler are much lower than those of the rocker type sprinkler,which can effectively save water and energy.It can be considered that overall hydraulic performance of the jet-pulse sprinkler is better than that of the rocker-type nozzle at 0.20 MPa～0.35 MPa. |
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