Structure Design And Experimental Research Of Negtive Pressure Feedback Jet Sprinkler

There is much water consumption in agricultural production in China,and the sprinkler can effectively improve the utilization rate of water resources.Although the impact sprinkler is cheap and adaptable,its structure is complex and its service life is relatively short which results in unstable work and decrease of sprinkling uniformity.Therefore,it is of great significance to study the driving mechanism and spraying method of the sprinkler.In this dissertation,the structure and performance of negtive pressure feedback jet sprinkler were studied by means of theoretical research,numerical simulation and experimental study.The main research contents of the study are as follows:?1?The numerical simulation of 125 groups of jet sprinkler with different jet element structures was carried out by means of controlling variable method.The design intervals of three important structural parameters were obtained.Among them,the potential difference ratio was 0.375⁰.525,the side wall angel was 10°¹2°,the split distance ratio was 7⁹ and the influence of these structure parameters on pulse characteristics was obtained.The optimal structure of pulse characteristics was obtained by orthogonal test,and the influence of structures on pulse characteristics in sequence was further obtained,wherein the factors influencing the pulse frequency were the split distance ratio,the potential difference ratio,the side wall angle,the factors influencing the pressure amplitude were the potential difference ratio,the split distance ratio and the side wall angle.The structure size of the optimum pulse characteristics was the potential difference ratio 0.450,the side wall angel10°and the split distance ratio 7.Then,the characteristics of internal flow field,outlet pressure and internal pressure of jet sprinkle were studied.The influence of working pressure on pulse characteristics was obtained.?2?The experimental prototypes of various components of jet sprinkler were designed and processed.The hydraulic performance of 16 groups of jet sprinkler with the diameters of 3⁵ mm,the spraying angles of 20⁵0°and the relative sprinkler tube lengths of 6¹0 at the working pressure of 0.20⁰.35 MPa was carried out,and the hydraulic performance parameters such as inlet flow rate,range,water distribution,sprinkler intensity,uniformity coefficient and rotation characteristics were obtained.The influence of the working pressure,the nozzle diameter,the spraying angle and the relative sprinkler tube length on the hydraulic performance parameters was also analyzed.The results showed that the spraying angle and the relative sprinkler tube length had little effect on the inlet flow rate.The working pressure,the nozzle diameter,the spraying angle and the relative sprinkler tube length had great influence on the range,the sprinkler irrigation intensity and the uniformity coefficient.The precipitation was mainly distributed as"triangle","trapezoid"and"saddle"shape.The rotation period was 8²58 s and the rotation deviation was 0.00⁰.19.?3?Through orthogonal test and comprehensive scoring method,it was found that the order of factors influencing the comprehensive hydraulic performance in sequence was the main relative sprinkler tube length×the secondary relative sprinkler tube length,the main nozzle diameter×the secondary nozzle diameter,working pressure and the spraying angel.The working pressure of the optimum hydraulic performance was 0.25 MPa,the structure size of the optimum hydraulic performance was the main nozzle diameter×the secondary nozzle diameter 5×4,the spraying angle 30°and the relative sprinkler tube length×the secondary relative sprinkler tube length 6×6.?4?The jet pulse characteristics obtained by numerical simulation were verified by high-speed photography experiments.The test deviation of pulse frequency was 0.0⁴.0 Hz,and the test deviation of inlet flow rate was 0.03⁰.17 m³?h^-1,which indicates that the numerical simulation results were reliable.Finally,the hydraulic performance of jet sprinkler and PY₂10 impact sprinkler under four working pressures was tested by comparative experiments.The results showed that jet sprinkler has good research value.