负压反馈射流喷头主副喷嘴直径及流道结构参数的优化

负压反馈射流喷头是一种基于射流脉冲特性设计的全圆旋转灌溉喷头。喷头的主副喷嘴尺寸组合对该型喷头脉冲特性和水力性能影响较大。为确定主副喷嘴直径的设计区间及各流道结构参数对喷头性能的影响,首先利用单因素数值模拟方法确定具有良好脉冲效果的主副喷嘴直径设计区间,再以进口流量和射程为评价指标,进行了九因素四水平正交试验。采用极差分析法和相对影响指数评价法处理正交试验结果,得到了喷头主副喷嘴最佳尺寸组合与内部最优流道参数,加工优化后样机进行优化前后喷头水力性能对比试验和数值模拟验证试验。结果表明,在0.15～0.30 MPa工作压力范围内,主、副喷嘴直径的设计区间分别为4.0～4.5 mm、3.5～4.5 mm,最优流道结构具体参数为位差比0.475、侧壁倾角12.0°、劈距比9.0、深宽比2.5、相对曲率半径比3.0、主副喷管相对长度组合8 cm×6 cm、主副喷嘴组合4.5 mm×3.5 mm、仰角30°。优化后的样机比优化前的进口流量降低了12.1%～14.6%、射程增加了6.5%～9.4%,优化后喷头的中近程降水深较优化前减小,远处降水深增加。优化后试验值与模拟值的归一化均方根误差指标分别为4.2%和6.7%,说明优化效果较好,水体模型精度较高。研究提出的最优流道结构参数及研究过程可为喷头后续设计提供参考。

Optimization of the diameters of main nozzle and sub-nozzle and flow channel structure parameters of negative pressure feedback jet sprinkler

The negative pressure feedback jet nozzle is a full circle rotating irrigation nozzle designed based on the jet pulse characteristics. The size combination of the main and auxiliary nozzles of the nozzle has a great influence on the pulse characteristics and hydraulic performance of the nozzle. A reasonable combination of the main and auxiliary nozzles can greatly improve the pulse effect, thereby improving the hydraulic performance of the nozzle, and ensure the optimal flow path. In order to have the best hydraulic performance of the structural parameters, the inlet flow rate and range are selected as evaluation indicators. The smaller the inlet flow, the lower the intensity of sprinkling irrigation At the same time, 9 structural parameters are fully considered as orthogonal test parameters. In order to determine the design interval of the main and auxiliary nozzle diameters and the influence of each flow channel structure parameter on the performance of the nozzle, a single factor numerical simulation method was used to determine the design interval of the main and auxiliary nozzle diameters with good pulse effect. A total of 108 sets of simulations were carried out. The 22 groups were defined as better pulse effects, and the inlet flow rate and range were used as evaluation indicators, and a orthogonal test was carried out. For the 32 sets of arrangement data obtained by orthogonal experiments, the test results are processed by the range analysis method and the relative influence index evaluation method, and the optimal parameters combination of the main and auxiliary nozzles of the nozzle and the optimal internal flow channel parameters were obtained. The runner structure parameter model was processed into a prototype and an experimental platform was set up at Jiangsu University. The comparison test was carried out to verify the reasonability of numerical simulation and the hydraulic performance of the nozzle before and after optimization. The results showed that within the working pressure range of 0.15-0.30 MPa, the design intervals of the main and auxiliary nozzle diameters are 4.0-4.5 mm and 3.5-4.5 mm respectively, and the specific parameters of the optimal flow channel structure are the displacement ratio of 0.475, the sidewall inclination angle of 12.0°, split length ratio 9.0, aspect ratio 2.5, relative curvature radius ratio 3.0, relative length combination of main and auxiliary nozzles 8 cm×6 cm, combination of main and auxiliary nozzles 4.5 mm×3.5 mm, elevation angle 30°. The optimized prototype test value was 12.1%-14.6% lower than the pre-optimized test value, and the range was increased by 6.5%-9.4%. After optimization, the normalized root-mean-square error indexes of the experimental value and the simulated value were 4.2% and 6.7%, respectively, indicating that the optimization effect was better and the accuracy of the water model was higher. The middle and short range water depth of the nozzle reduced compared with before optimization, and the distant water depth of the nozzle increased compared with before optimization. The optimal flow channel structure parameters and research process can provide reference for the subsequent design of the nozzle.