结点局部能量损失对管网水力计算的影响

Influence of local energy loss at junctions on hydraulic calculation of pipeline network

对于管径较大、管段长度较短的管网,结点处的动量交换和局部能量损失显著影响管网中管段通过流量的计算结果。进行管网水力计算时,忽略结点处的局部能量损失或采用不变的局部能量损失系数均是不合适的。文中分别应用三种计算方法,即忽略结点处局部能量损失、采用恒定不变的结点局部能量损失系数,以及根据试验成果所得的与水流条件有关的半经验公式,针对短管段构成的管网系统进行了计算比较,管段流量的计算结果相差很大。研究结果还表明,与同一结点相接的各管段间存在显著的能量交换,因此,忽略或采用恒定不变的能量损失系数均不能正确地反映这些水流现象。

The calculation result of passed flow rate in pipe section of pipeline network is significantly influenced by the momentum exchange and the local energy losses at junctions for the pipeline network comprised of the pipes of larger diameter and shorter length. During the hydraldic calculation on pipeline network, it is unacceptable to neglect local energy loss or to adopt constant local energy loss coefficients. A calculation comparison on the pipeline network system consisting of pipe sections of short length is made herein with three calculation methods respectively, i.e. neglecting the local energy loss at junctions; adopting constant local energy loss coefficients and the semi-empirical relationships based on experimental data related to the flow conditions, from which the calculated results for the flow rates of the pipe sections are largely deviated. The study result also shows that there is significant energy exchange between all the pipe sections connected to the same junction, therefore, those flow phenomenon can not be accurately reflected if neglecting or adopting the constant energy loss coefficients.