偏心环空0-4 °倾角两相流数值模拟
Two-phase flow simulations at 0-4 degrees inclination in an eccentric annulus
摘要：
在偏心环空中进行了多相流模拟。对于外筒和内筒，环形空间的尺寸分别为0.1和0.05 m，混合物速度在1.2和4.2 m/s之间。模拟进行了比较，在能源技术研究所进行的完全偏心和完全同心的实验。本文的目的是探讨持液率和内管位置对压力梯度和流态的影响。比较表明，移动的管道从一个完全偏心的部分偏心配置有一个巨大的影响的压力梯度。在所有情况下，内管从完全偏心的几何形状改变为较小偏心的配置，我们注意到平均压力梯度增加了48 - 303\ %。相比之下，管道从同心配置移动到更偏心配置的情况下，导致压力梯度变化不太剧烈。2例在平均、最大和最小压差实验结果的22%范围内，而最后2例分别超过最小和平均压差25 - 250%。我们很少观察到流动状态的变化作为移动内管的影响; 8个水平案例中有2个表明从波浪流过渡到段塞流或明显更大的波浪。最突出和最常见的差异是改变段塞和波的频率。通过模拟，我们注意到，有一个增加的压力梯度伴随着增加的持液率分数时，相平均速度相同。对应于0.177、0.244、0.063和0.073的持液率增加分数，对于相同混合物流速和网格密度的每种情况，模拟压力梯度的增加分别为80、300、614和367 Pa/m或116、244、61.5和25%。
英文摘要：
Multiphase flow simulations were run in an eccentric annulus. The dimensions of the annulus were 0.1 and 0.05 m for the outer and inner cylinders, respectively, and the mixture velocities were between 1.2 and 4.2 m/s. The simulations were compared with fully eccentric and completely concentric experiments conducted at the Institute for Energy Technology. The purpose of this paper is to explore the effect of the holdup fraction and interior pipe's position on the pressure gradient and flow regime. The comparisons indicate that moving the pipe from an entirely eccentric to a partially eccentric configuration has a drastic impact on the pressure gradient. In all cases where the inner pipe was changed from a completely eccentric geometry to a less eccentric configuration, we notice an increase of 48-303 \% of the mean pressure gradient. Comparatively, cases, where the pipe was moved from a concentric to a more eccentric configuration, result in less drastic pressure gradient changes. 2 cases were within 22 \% of the experimental results for mean, max, and min pressure gradient, while the last two cases exceeded the minimum and mean pressure gradients by 25-250 %, respectively. We rarely observed a change of flow regime as an effect of moving the inner pipe; 2 out of the 8 horizontal cases indicate transition from wavy flow to slug flow or significantly larger waves. The most prominent and frequent discrepancies identified were altered slug and wave frequencies. Through the simulations, we notice that there is an increased pressure gradient accompanying an increased holdup fraction when the phase-averaged velocities were the same. Corresponding to a fractional holdup increase of 0.177, 0.244, 0.063, and 0.073, the increase in simulated pressure gradient for each case of the same mixture flow rate and mesh density was 80, 300, 614 and 367 Pa/m respectively or 116, 244, 61.5 and 25 %.
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