低压滴灌管水力特性试验研究
发布时间：2018-10-16 21:34
【摘要】：利用理论分析与试验相结合方法，在分析毛管进口压力、铺设坡度、滴孔间距、铺设长度等因素基础上，研究了诸要素对低压滴灌系统灌水均匀度、滴孔出流特性、沿程水头损失、沿程压力分布规律等的影响，主要得出以下成果： 1）滴灌管单孔平均流量在同一工作压力下随铺设长度的增大而减小，随着铺设长度的增加，平均流量变化比较缓慢；随压力水头的增加而增加，且变化比较剧烈；随滴孔间距的加大而增加，且增加的速度随孔距的增大而增大，孔距1.2m的孔口流量最大，孔距0.6m的孔口流量最小，孔距0.9m与孔距0.6m之间的孔口流量差异较小。 2）孔距1.2m的滴灌管的流量系数k随铺设长度的增大先减小后增大，在铺设长度40m时流量系数最小；而孔距0.6m、0.9m的滴灌管的流量系数随铺设长度的增大而减小。滴灌管的流态指数x随铺设长度的增大先增大后减小，孔距0.6m、1.2m的滴灌管在铺设长度为40m时流态指数x最大；孔距0.9m的滴灌管在铺设长度为30m时流态指数最大。 3）在相同的压力水头下，灌水均匀度随毛管铺设长度的增大而呈降低趋势，铺设长度越短，毛管灌水均匀性越好。在相同的铺设坡度下灌水均匀度随着毛管进口压力的增大呈增大趋势。灌水均匀度随着坡度的增大呈先增大后减小的趋势，，当i在-1‰～1‰范围内变化时，灌水均匀度随着铺设坡度的增大而增大，增加幅度较大，并在1‰坡度时均匀度达到峰值；当i大于1‰时，灌水均匀度随着铺设坡度的增大反而减小，但减小的幅度较小。 4）用常压公式计算毛管水头损失与实测值相差较大，理论值均小于实测值。并且实测值与规范推荐公式计算值的比值随着工作压力的增加在缩小，且随着压力的增大，比值趋近于1。在试验的低压条件下，通过对实测值与计算值的比值与进口压力做回归分析，得水头损失修正系数，拟合相关性较好。当计算结果要求不是很精确时，采用进口压力水头对水头损失计算公式基本可达到修正的目的。 5）根据变质量动量方程，建立了滴灌多孔管在任意点位置的压力水头计算公式，利用该公式可计算毛管首孔断面、末端断面和任意断面处的压力水头。 6）从微灌工程水头损失计算的通用公式出发，通过对孔口出流实际水头线的简化，用微分法建立了毛管沿程水头损失的一般方程，根据能量方程得出了沿程压力水头的计算公式，通过与动量法建立的压力水头方程的比较，指出本模型简化的合理性，且给出了在不同坡度下，毛管允许最大铺设长度Lm的确定方法。
[Abstract]:Based on the analysis of capillary inlet pressure, laying slope, drop hole spacing, laying length and other factors, the effects of various factors on irrigation uniformity and outlet flow characteristics of low pressure drip irrigation system were studied by combining theoretical analysis and test. The main results are as follows: 1) under the same working pressure, the average flow rate of single hole decreases with the increase of laying length, and increases with the increase of laying length. The average flow rate changes slowly, increases with the increase of pressure head, and increases with the increase of the spacing of droplets, and the increasing velocity increases with the increase of hole spacing, and the flow rate of the hole with 1.2m hole spacing is the largest. The flow coefficient k of the drip irrigation pipe with 1.2m hole distance decreases first and then increases with the increase of laying length, and the flow coefficient is the smallest when the length of laying is 40m, the flow rate of the drip irrigation pipe with the hole distance of 0.6 m is the smallest, and the flow coefficient between the hole distance of 0.6 m and the hole distance of 0.6 m is smaller than that of the hole distance of 0.6 m. However, the discharge coefficient of the drip irrigation pipe with a distance of 0.6 m to 0.9m decreases with the increase of the laying length. With the increase of laying length, the flow state index x of the drip irrigation pipe increased first and then decreased, and the flow state index x of the drip irrigation pipe with 0.6 m ~ 1.2m hole distance was the largest when the laying length was 40 m. Under the same pressure water head, the irrigation uniformity decreased with the increase of the laying length of the capillary tube. The shorter the laying length, the better the water uniformity of the capillary tube was. 3) when the laying length was 30 m, the flow index was the largest. 3) under the same pressure water head, the irrigation uniformity decreased with the increase of the laying length of the capillary tube, and the shorter the laying length was, the better the water uniformity of the capillary tube was. The uniformity of irrigation increased with the increase of capillary inlet pressure at the same laying slope. The uniformity of irrigation increased first and then decreased with the increase of slope. When I varied in the range of -1 鈥
本文编号：2275690
[Abstract]:Based on the analysis of capillary inlet pressure, laying slope, drop hole spacing, laying length and other factors, the effects of various factors on irrigation uniformity and outlet flow characteristics of low pressure drip irrigation system were studied by combining theoretical analysis and test. The main results are as follows: 1) under the same working pressure, the average flow rate of single hole decreases with the increase of laying length, and increases with the increase of laying length. The average flow rate changes slowly, increases with the increase of pressure head, and increases with the increase of the spacing of droplets, and the increasing velocity increases with the increase of hole spacing, and the flow rate of the hole with 1.2m hole spacing is the largest. The flow coefficient k of the drip irrigation pipe with 1.2m hole distance decreases first and then increases with the increase of laying length, and the flow coefficient is the smallest when the length of laying is 40m, the flow rate of the drip irrigation pipe with the hole distance of 0.6 m is the smallest, and the flow coefficient between the hole distance of 0.6 m and the hole distance of 0.6 m is smaller than that of the hole distance of 0.6 m. However, the discharge coefficient of the drip irrigation pipe with a distance of 0.6 m to 0.9m decreases with the increase of the laying length. With the increase of laying length, the flow state index x of the drip irrigation pipe increased first and then decreased, and the flow state index x of the drip irrigation pipe with 0.6 m ~ 1.2m hole distance was the largest when the laying length was 40 m. Under the same pressure water head, the irrigation uniformity decreased with the increase of the laying length of the capillary tube. The shorter the laying length, the better the water uniformity of the capillary tube was. 3) when the laying length was 30 m, the flow index was the largest. 3) under the same pressure water head, the irrigation uniformity decreased with the increase of the laying length of the capillary tube, and the shorter the laying length was, the better the water uniformity of the capillary tube was. The uniformity of irrigation increased with the increase of capillary inlet pressure at the same laying slope. The uniformity of irrigation increased first and then decreased with the increase of slope. When I varied in the range of -1 鈥
本文编号：2275690
本文链接：https://www.wllwen.com/kejilunwen/shuiwenshuili/2275690.html
