Abstract: Gas-liquid stirred tanks are widely used in chemical, pharmaceutical, and biochemical processes, where efficient dispersion of gas into liquid is essential for optimal mass transfer performance. Although various impeller designs have been developed, the gas dispersion characteristics of non-conventional impellers such as the double-bend wide-skewed (DBWS) impeller remain insufficiently explored. Based on a coupled computational fluid dynamics and population balance model (CFD-PBM), the gas holdup of DBWS was investigated under different rotational speeds and aeration rates. Additionally, the dispersion characteristics of DBWS impeller were compared with RT impeller under a specific operating condition. It was found that increasing rotational speed and aeration rate generally led to a higher gas holdup. However, excessively high aeration rates resulted in unstable gas dispersion, which negatively affected mass transfer reliability. Compared to the RT impeller, the DBWS impeller achieved a significantly higher stable gas holdup, despite requiring a longer time to reach steady state. A notable advantage of DBWS impeller was its ability to generate a larger proportion of fine bubbles in the 0~2 mm range, which promoted more efficient gas-liquid contact. In the DBWS impeller vessel, gas was primarily distributed between the two impellers and effectively contacted the liquid in both the mixing zone and near the vessel wall. Conversely, gas in the RT impeller vessel accumulated mainly near the shaft and impeller blades. In addition, the DBWS impeller produced slender and continuous vortex structures that effectively suppressed bubble coalescence. In contrast, the RT impeller formed intense and localized vortices near the blades, causing gas to accumulate behind the blades and form cavities, thereby reducing dispersion efficiency. Generally, these results demonstrated that DBWS impeller exhibited superior gas dispersion capability compared to the RT impeller, offering better gas distribution and higher gas holdup stability. These findings offer valuable insights for the practical engineering application of double-bend wide-skewed impellers.

Key words: gas-liquid stirred tank, CFD-PBM, gas-liquid two-phase flow, dispersion characteristics

摘要： 基于计算流体力学-群体平衡模型(CFD-PBM)方法，对双折弯宽斜叶(DBWS)桨气液搅拌釜内不同转速(N)和通气速率(QG)的气含率进行了模拟研究，并在特定工况下对DBWS桨与Rushton (RT)桨的分散特性进行对比研究。结果表明，DBWS桨釜内气含率均会随着转速和通气速率增大而增大，但过大的通气速率会使釜内气含率失稳，从而影响气液传质稳定；与RT桨相比，DBWS桨的气体分散效果更好，DBWS釜内的气含率稳定值更大，0~2 mm的小尺寸气泡占比明显更高，气体能在全釜范围内与液体进行更有效地接触，另外，DBWS桨产生的涡结构更为细长且连续，这可以有效避免气泡聚并形成气穴。研究结果可为双折弯宽斜叶桨在实际工程中的应用提供参考。

关键词: 气液搅拌釜, 计算流体力学-群体平衡模型, 气液两相流, 分散特性