温室滴灌系统支管水力性能影响因素试验研究

Experiment on the Hydraulic Performance of Branch Line in Drip Irrigation

通过室内试验研究分析了入口压力、支管长度、毛管间距3个因素对滴灌系统中支管水头损失及沿程压力分布的影响。结果表明:支管上的水头损失随着支管长度和入口压力的增大而增大,随毛管间距的增大而减小,但入口压力增大也同时使得支管沿线压力分布更为均匀。毛管间距0.6、0.9和1.2m条件下,满足水力偏差要求的支管最大铺设长度分别为20、40和60m。支管沿程压力分布曲线服从三次多项式关系,R2均在0.99以上。对支管上水头损失的构成进行了分析,表明局部与沿程水头损失之比fc随支管长度的增加、毛管间距的减小而增加,部分工况下fc会超过1;fc随首部压力的变化较为复杂,与具体的管网铺设s条件相关。多孔系数与来流条件有关,利用克里斯钦森公式计算出的多孔系数比实际值略微偏大,入口雷诺数从22 707增加至50 846时,克里斯钦森公式计算值与实测值之比从1.107降至1.068,表明入口雷诺数越大,克里斯钦森公式的计算精度越高。

The effects of operating pressure, pipe length and lateral spacing on the head loss and longitudinal pressure distribution of branch pipe in a drip irrigation system are studied by a laboratory testing. The results show that the total head loss increases with the increase of operating pressure and pipe length, but decreases with the increase of lateral spacing. It is worth mentioning that a larger operating pressure conduces to a more uniform longitudinal distribution. The maximum of permissive laying length is 20, 40 and 60 m with the lateral spacing 0. 6, 0. 9 and 1.2 m, respectively. The pressure distribution along the branch pipe obeys a cubic polynomial well and the R2 is above 0. 99 without exception. The constitution of total head loss is calculated and analyzed, the results show that the local-to-friction loss ratio increases with the increase of pipe length while decreases with the increase of lateral spacing, in some cases, the ratio is even greater than 1. The relation between the ratio and pressure is very complicated and depends on the laying cases. The factor of multiple outlets is related to the inlet flow condition, and the values calculated by Christiansen formula are larger than the measured ones, and become more precise with the increase of the inlet Reynolds numbers.