低压地下与地表滴灌滴灌带水力性能对比试验

为研究低压条件下地下毛管的水力性能与灌水均匀度的变化规律,以新疆大田地下滴灌系统作为研究对象,支管入口压力在1.4~6.55 m之间,在支管的首部、中部和尾部分别对地下和地表毛管进行测试,比较流量、工作压力和总水头损失等参数间的关系。结果表明:1)可以通过压力与流量判断毛管工作是否正常。2)地下毛管在土壤基质势驱动滴头出流时,大于地表毛管流量,相对地表毛管流量增加0.12~0.9,并且增加比例随压力降低而增大。3)90%的正常地下毛管的工作压力要小于地表毛管,压力折减系数在(-10%,0)的概率是70%。4)用总水头损失、勃拉休斯公式及多口系数推求毛管考虑局部水头损失的加大系数,地表毛管平均值在1.32~5.94之间,地下毛管平均值在1.37~2.18之间,二者均随压力降低而增大;土壤基质势作用使地下毛管流量增大,导致地下毛管的加大系数比地表毛管小。5)地表管网的灌水均匀度随压力降低而降低;土壤基质势的作用提高了地下管网的均匀度,压力偏差率比地表管网低0.62%~3.44%,流量偏差率比地表管网低8.15%~22.4%。该研究可为低压地下滴灌系统的设计与管理提供科学依据。

Comparison test on drip irrigation tape hydraulic performance under low-pressure between subsurface drip system and surface drip system

Abstract: With the wide spread of drip irrigation, low-pressure subsurface drip system has come into notice as it can reduce the operation cost and improve water and fertilizer use efficiency, and it has become an emerging trend in drip technology development. A field experiment was carried out in Xinjiang to investigate the variation law of hydraulic performance and irrigation uniformity in subsurface drip system under low pressure. We chose lateral capillary from the head and end of the main branch to be the representatives, as well as the middle ones. The inlet pressure of branch pipe was set between 1.40 and 6.55 m; then we compared subsurface drip system with surface drip system under the same conditions in relation to flow rate, working pressure, and total head loss. The results indicate that: 1) The operation status of laterals can be monitored by working pressure and flow rate in the drip irrigation system. 2) When the emitter outflow is driven by the soil matric potential, the flowrate of underground laterals is larger than that of the surface laterals, and the coefficient of flow variation is increasing by 0.12 to 0.9, and it keeps increasing with the decrease of working pressure. 3) When comparing the working pressure of subsurface drip system with that of the surface drip system, 90% of subsurface drip laterals are less than that in the surface drip irrigation system, and the variation coefficient of working pressure is from ?10% to 0 with the probability of 70%. 4) The increasing coefficient considering local head loss of laterals (ICCLHLL) is calculated by using the total head loss, the Blasius formula, and the flow from multiple outlets, and the value of surface drip system is within the range of 1.32-5.94, while range between 1.37 and 2.18 for subsurface drip system, and the ICCLHLL increases with the decrease of working pressure. The flow rate of subsurface laterals keeps increasing under the influence of the soil matric potential, which leads to the decrease of ICCLHLL in surface drip laterals. 5) When decreasing working pressure, the irrigation uniformity of surface drip system will also decline. The soil matrix potential improves the irrigation uniformity of subsurface drip system. The deviation rates of working pressure and flow rate in the subsurface drip system are 0.62%-3.44% and 8.15%-22.4% lower than those in the surface drip system, respectively. The research can provide a scientific basis for design and management of low-pressure subsurface drip irrigation.