虹吸管内气泡流流动水力特性

Flow Hydraulic Characteristics for the Bubble Flow in Siphon

针对非驼峰式大真空度水平管段较长的正虹吸管道进行了系列实验,在虹吸管内呈现气泡流流型状态下,量测了不同安装高度、不同水头差条件下的虹吸管流动压降、过流能力和截面含气率。实验结果表明,气泡流流型状态下虹吸管道过流能力及压降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泡流流型状态下的虹吸管过流能力和流动压降。基于实验结果分析了影响气泡流过流能力和压降大小的因素,结果表明气体存在对流动沿程阻力系数影响很小,可忽略不计,过流能力和压降计算仍可采用单一液相流动沿程阻力系数。不同安装高度虹吸管的流量变化和压降变化仅是由于气泡存在占据一定的过水断面积,使得实际过水断面积小于管道断面积。结合实验结果和数值分析,推导出适用于气泡流流型状态的伪空化现象明显、安装高度不大于8m、水平管段较长、考虑含气率大小的虹吸管过流能力和压降计算公式。经检验,公式计算误差小于±5%。

The siphon pipe with non-hump vaccum degree horizontal tubulation was systematically tested,the different installation height,siphon flow pressure drop in different water head difference condition,conveyance capacity and section air void were measured.The test results showed that the conveyance capacity in siphon and pressure drop decreased with the increase of installation height in the siphon under the condition of bubble flow pattern.The conveyance capacity and flow pressure drop could not be calculated with the fromula of conventional pressuried pipe flow.According to the experiment results,the factors affecting the conveyance capacity of bubble flow and pressure drop size were analyzed.The results showed that the gas had little effect on the parameters of flow resistance,which could be negleted,and coefficient of frictional resistant of liquid flow also could be used when conveyance capacity and pressure drop were caculated.The flow and pressure of siphon with different installation height changed only because of a certain discharge section occupied by air bubble,which made the actual discharge section be less than cross-sectional area of the pipe.According to the test results and numerical analysis,it was developed that the false appearance,installation height suitable for bubble flow were greater that 8m,after the modification,the error of the calculating formula was less than ±5%.