考虑断面形变的贴片式滴灌带局部水头损失研究

Study on local head-loss of the drip irrigation tape equipped with integrated in-line emitters by considering cross-section deformation

为研究断面形变对内镶贴片式滴灌带局部水头损失的影响,选取6种不同壁厚滴灌带,通过试验查明滴灌带断面形状与壁厚及压力的关系,据此采用数值模拟和量纲分析构建滴灌带局部水头损失计算数学模型。结果表明:滴灌带断面形状随压力变化差异明显,低压条件下滴灌带扁平断面可用椭圆近似计算;提出了变断面内镶贴片式滴灌带局部水头损失计算数学模型,滴灌带局部水头损失与滴灌带断面扁平系数的0.867次方成反比;实际工程中在计算滴灌带水头损失时,应区分低压和非低压2种工况,当低压条件下滴灌带出现非圆断面时,应考虑滴灌带断面形变对滴头水头损失的影响,可参考本文算例分析中局部水头损失占沿程水头损失比值15%估算,或在圆断面计算的基础上乘以值约为1.5的修正系数。

In order to study the effect of cross-section deformation on local head-loss in in-line drip irrigation tape,in this paper,six different wall thickness of drip irrigation tapes were selected,the relationship between cross-section deformation and the wall thickness and pressure were obtained by the experiment.On this basis,the influencing factors of local head-loss in drip irrigation tape were obtained by numerical simulation and dimension analysis.The results showed that the shape of the cross-section of the drip irrigation tape varied with the pressure,low-pressure conditions,the cross-section of the drip irrigation tape was nearly elliptical.The expression of local head-loss in in-line drip irrigation tape with variable cross-section was given,and the local head-loss in the drip irrigation tape was inversely proportional to the 0.867 power of the flatness of the drip irrigation tape.In the actual project,when calculating the head-loss of the drip irrigation tape,it is necessary to distinguish between low pressure and non-low pressure working conditions.When the non-circular cross-section of the drip irrigation tape appeared under low pressure,the influence of the cross section deformation of the drip irrigation tape on the head-loss of the drip irrigation tape should be considered.It can be estimated by referring to the 15%ratio of the local head-loss to the friction head-loss in the analysis of the calculation example in this paper,or multiplying it by a correction factor of about 1.5 based on the calculation of the circular section.