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首页> 外文会议>4th International Pipeline Conference, Sep 30-Oct 3, 2002, Calgary >A Numerical Study of Dispersed Air Bubbles in a Hydrotransport Pipeline Flow
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A Numerical Study of Dispersed Air Bubbles in a Hydrotransport Pipeline Flow

机译：输水管道中分散气泡的数值研究

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摘要

Different flow pattern maps and theoretical models were employed to determine the flow velocity needed to provide the dispersed-bubble flow in a hydrotransport pipeline. Comparison and analysis of the results has been carried out. The maximum and minimum bubble sizes were determined by semi-experimental methods. A log-normal function was employed to describe the bubble size distribution. A model for the bubble size change in the turbulent pipe flow was applied to study the evolution of the overall bubble size distribution. This model takes into account the competing factors influencing the bubble size: 1) dissolution (turbulent diffusion) of air in the liquid, causing bubble shrinkage; 2) pressure drop along the pipeline, causing bubble growth. Numerical analysis shows that the bubble dissolution rate strongly depends on the initial air hold-up and initial bubble size. An increase of air hold-up leads to a fast decrease of the dissolution rate. At sufficient high air hold-ups, the dissolution effect becomes negligible and air bubble sizes are dominantly controlled by the pressure drop. Smaller bubbles have higher dissolution rates than larger ones. Compared with a pure liquid flow under the same flow conditions, the effect of air hold-up is stronger in the slurry flow because of the smaller volume occupied by the liquid.
机译：使用不同的流型图和理论模型来确定在输水管道中提供分散气泡流所需的流速。结果进行了比较和分析。最大和最小气泡尺寸通过半实验方法确定。使用对数正态函数来描述气泡尺寸分布。湍流管道中气泡尺寸变化的模型用于研究总体气泡尺寸分布的演变。该模型考虑了影响气泡大小的竞争因素：1）空气在液体中的溶解（湍流扩散），导致气泡收缩； 2）沿管道的压力下降，导致气泡增长。数值分析表明，气泡的溶解速度很大程度上取决于初始持气量和初始气泡大小。空气滞留量的增加导致溶解速率的快速降低。在足够高的空气滞留量下，溶解效果可忽略不计，气泡大小主要受压降控制。较小的气泡比较大的气泡具有更高的溶解速率。与在相同流动条件下的纯液体流相比，由于液体所占的体积较小，因此在浆液流中持气效果更强。

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