虹吸管内气团流流型时过流能力计算

该文针对非驼峰式正虹吸管道进行了系列试验,量测了不同安装高度、不同水头差时管内呈现气团流流型时的过流能力和截面含气率。试验结果表明,气团流流型下虹吸管道过流能力随虹吸管安装高度的增大而减小,不能采用常规有压管流公式计算气团流流型时虹吸管过流能力。基于试验结果分析了影响气团流过流能力的因素,结果表明气体存在对流动沿程阻力系数影响不可忽略,过流能力计算时不能直接采用单一液相流动沿程阻力系数。不同安装高度时虹吸管内过流面积减小不是导致输水流量减小的唯一因素,除了考虑过流面积减小对过流量的影响外,还应考虑含气率大小引起的μ_0或λ变化对流量的影响。结合试验结果和数值分析,推导出适用于气团流流型下伪空化现象明显、安装高度不大于8 m的水平管段较长考虑含气率大小的虹吸管流量系数计算公式,修正和完善了有压管流过流能力计算公式,经检验公式计算误差小于±7%。

The hydraulic characteristics for the bubble flow in siphon

This paper conducted a series of tests according to the non-hump siphon.The conveyance capacity and section void fraction were measured on different installation heights and head difference of air mess flow The results showed that the conveyance capacity decreased with the increase of installation heights.So that conventional pressurized pipe flow formula was not suitable for conveyance capacity of air mess flow in siphon.The influential factors of conveyance capacity were analyzed based on test results.The effect of gas existed and section void fraction to frictional resistant coefficient could not be neglected,and the single liquid phase formula of frictional resistant coefficient was not suitable for conveyance capacity.In addition the decreasing of area should be considered,the gas fraction which led μ0 or λ to be changed also should be considered.The results and numerical analysis method were combined to derive the calculations of flow coefficient which were suitable for air mass flow,pseudo-cavitation,installation height less than 8 m.And the calculations of conveyance capacity for pressure conduit were corrected and improved.The calculation errors were less than ±7％ by inspection.