Profile Optimization And Experimental Study Of Low Flowrate Negative Pressure Feedback Jet Nozzle

This thesis presents a novel negative pressure feedback jet nozzle designed by the wall switching effect of the jet,which shows great advantages in structure simplification,spraying uniformity,and life cycle.As a response to the strategic goals of sustainable development,energy efficiency enhancement has become one of the primary developing directions of the nozzle industries.It is worth noting that reducing flowrate and pressure is one of the most effective technical approaches for improving the overall efficiency of the nozzle.However,the inlet width of the existing products is large,which is not beneficial for the reduction of energy consumption,and thus is unable to meet the requirements of the mainstream market.In order to fix this situation,an optimization design of the low-flowrate negative pressure feedback jet nozzle coupled with the redesign of the structure of the driver board was carried out.The detailed information of this study is given as follows.（1）The single-factor analysis method was applied to simulate 125 different sample designs of low-flowrate negative pressure jet nozzle using the numerical approach,whose range of inlet width was determined in accordance with the Chinese standard GB/T 22999-2008.The analysis results illustrate that the nozzle with a position difference ratio in the range of 0.3 to 0.45,the sidewall inclination angle in the range of 8°to 12°,and the split distance ratio in the range of 6 to8,performs better in jet pulsation.Based on such conclusions,a nine-factor four-level orthogonal experiment was adopted to optimize the profile of the nozzle.The test samples were studied using the extreme difference analysis method with the objectives of flowrate and jet range,whose results demonstrated that the inlet width has the most significant impact on the flowrate and the combination of the primary and secondary nozzles shows the highest correlation with the jet range.Consequently,the optimal design parameters were determined by the correlation between the objectives and parameters.The specifications are listed as follows:the jet element inlet width is2mm,bit difference ratio is 0.40,the sidewall inclination angle is 12°,the split distance ratio is6.7,the primary and secondary transition bend radius of curvature is 25mm,the jet element inlet depth to width ratio is 2.5,the control channel width ratio is 0.7,the primary and secondary nozzle combination form is 2.5×1.9mm.（2）The single-factor analysis method was adopted to generate 16 different sample designs of the driver board,with the design parameters of the vertical length,the vertical width,and the inclined width.The optimized nozzle obtained in the previous step was manufactured for further hydraulic experiments coupled with these 16 samples.The result analysis indicated that the structure of the driver board has no effect on the nozzle range,flowrate,and irrigation intensity when the inlet pressure is in the range of 0.15 MPa to 0.30 MPa.However,it shows excellent correlations with the spraying water distributions and the irrigation uniformity.The spraying water moves from the near field to the middle field and then returns to the near field with the increase of the vertical length.The spraying water tends to distribute at the near field when the vertical width rises or the inclined width increases.Consequently,the nozzle has the optimum performance when the vertical length of the driver board is 3D₁（the diameter of the primary nozzle）,the vertical width is 3.5 D₁,and the inclined width is 1.0W_c or 1.1W_c（the vertical width of the driver board）.（3）A comparison experiment was executed between the optimized nozzle and the original product.After optimization,the jet range improved by 4.3～7.0%,the inlet flowrate decreased by2.5～7.2%,the intensity of the irrigation reduced by 16.6%～18.6%,and the uniformity coefficient of irrigation rise by 3.8～6.3%.（4）A hydraulic comparison experiment was carried out between the optimized negative pressure feedback jet nozzle and the traditional rocker nozzle.It reported that the presented nozzle shows essential advantages in all performance indices:the nozzle range increased by 5.4～10.3%,the inlet flowrate reduced by 4.6～8.4%,the intensity of the irrigation decreased by 20.4～27.7%,and the irrigation uniformity coefficient increased by 2.6～5.8%.