温室滴灌系统支管水力性能及简化计算研究

我国温室产业近年来发展迅猛,由于面积、种植结构与密度等与大田差异较大,沿用大田滴灌系统的设计方法已不适宜,需要根据温室的具体条件确定设计方法。根据我国普通单栋温室情况,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沿程压力分布的影响。结果表明:支管沿程压力分布的均匀性随支管长度的增加、毛管间距和首部压力的减小而降低。结合滴头的水力特性参数得出支管上的最大允许压力偏差为30.85%。毛管间距0.6、0.9和1.2m条件下,满足水力偏差要求的单栋温室支管最大铺设长度分别为20、40和60m。运用量纲分析方法将影响支管水头损失的基本量导出为3个无量纲量υd/ν、υ2/(g d)和L d/s2,通过多元回归建立支管水头损失的经验预测模型(R2=92.4%)。分析了支管能坡曲线的函数形式,回归得到了支管水头损失比和沿程压力分布模型。以上模型预测值与实测数据拟合效果良好,可用于温室滴灌系统水力计算及规划设计。

A Study on the Hydraulic Performance and Simplified Calculation of Branch Line in Drip Irrigation System

Greenhouse industry has got rapid development in recent years .Since greenhouse is quite different from field in the aspects of area ,planting structure and density ,the design idea of drip irrigation in field is not adaptable for greenhouse .In order to offer ref-erences to the design of drip irrigation in greenhouse ,the effects of operating pressure ,pipe length and lateral spacing on longitudinal pressure distribution of branch pipe in drip irrigation system are studied through a laboratory testing .The results show that the dis-tribution uniformity decreases with the increase of the pipe length ,but increases with the increase of lateral spacing and operating pressure .The largest permissive laying length of branch pipe is 20 m ,40 m ,and 60 m with the lateral spacing of 0 .6 m ,0 .9 m and 1 .2 m ,respectively .A model is developed by using dimensional analysis and multiple regression ,to predict head losses on branch pipe with three dimensionless variables ,namelyυd /ν,υ2/(g d) and L d /s2 .The energy gradient curve is analyzed and developed . The prediction models mentioned above is precise enough to be applied in actual operation .