虹吸管气液两相流压降特性试验

Experiment on pressure drop characteristics of air-liquid two phase flow in siphon pipeline

通过系列试验量测了不同安装高度、不同水位差时虹吸管水平管段的压降、含气率及过流量,探讨和分析了虹吸管气液两相流压降的变化规律及气液两相流流型不同时影响管道压降的因素。结果表明,气液两相流管道压降与液相满流时压降规律相同,即压降值随管道水头的增大而增大;但是,与液相有压管流不同,水位差一定时压降值随安装高度的增大而减小。当虹吸管内为气泡流时,气泡存在对沿程阻力系数λ影响很小,可忽略不计。管道实测压降小于计算值的原因是气液两相压降减小率等于流速减小率。当虹吸管内为过渡流和气团流时,气液两相压降减小率与流速减小率相差较大,实测压降的减小不仅与流速减小有关,含气率的大小对气液两相压降的影响也不可忽略,含气率的增大使气液两相流动阻力增大,即压降增大。

Through a series of experiments, the pressure drop, air content and flow rate of the horizontal section of the siphon pipeline under the conditions of various installed heights and various water level differences are measured, and then the changing law of the pressure drop of air-liquid flow in siphon pipeline and the factors to impact the pressure drop in pipeline when the pattern of the air-liquid flow is different are discussed and analyzed. The result shows that the pressure drop inside of the air-liquid two phase pipeline is identical with the pressure drop law when the liquid phase flow is full inside of the pipeline, i. e. the pressure drop value is increased along with the increase of water head; however, it is different from the pressure liquid phase flow in pipeline, i. e. when the water level is of a certain value, the pressure drop value is decreased along with the increase of the installed height. During bubble flow inside of siphon pipeline, only less impact is there from the bubble on the resistance coefficient A along the pipeline, and then it can be neglected. The cause of the measured pressure drop below its calculated value is that the reduction rate of the air-liquid two phase flow pressure drop is equal to that of the flow velocity. When transient flow and bubble flow are inside of the pipeline, the difference between the reduction rate of air-liquid two phase flow pressure drop and that of the flow velocity is larger, thus the reduction of the measured pressure drop is not only related to the reduction of the flow velocity, but the impact from the air content on the air-liquid two phase flow pressure drop can also be neglected, while the increase of the air content makes the flow resistance of the air-liquid two phase flow increased, i. e. the pressure drop increases.