液相中单气泡传质影响规律的数值模拟研究

Numerical Study on Mass Transfer Characteristics of a Single Bubble Rising in Liquid

摘要

气液传质过程是废水处理、吸收分离及生物曝气等多种工业生产过程中的关键步骤．界面传质速率的预测精度受界面性质复杂、模型精度以及实验测量精度等因素的影响，尤其在气泡流系统中，气泡表面显著的可变形特性进一步加剧了传质机制的复杂性，造成了传质速率难以准确预测，为传质设备的开发带来了极大的挑战．为此，本文采用基于 VOF 法的新型界面传质算法对伴有传质的气泡自由上升过程进行严格模拟．该算法利用统一的单场公式，可同步计算气泡的局部体积变化，适用于研究伴有传质的单气泡自由上升过程．通过对模拟结果进行分析，本文获得了不同厄特沃什数(Eo)和莫顿数(Mo)条件下气泡的运动行为，以及不同施密特数(Sc)下气泡传质特性；探讨了气泡变形、上升路径、局部流场对气泡传质速率以及浓度分布的影响．研究结果表明，气泡传质速率及浓度分布与气泡的动态行为密切相关，气泡形状与运动路径的不稳定性可促进气液间传质，同时气泡运动诱发的液相漩涡会显著改变液相中溶质的浓度分布．本研究为深入理解气液界面传质机理提供了理论支撑．

Abstract

Gas-liquid mass transfer is a critical step in various industrial processes，including wastewater treatment，absorption separation，and biological aeration. However，the prediction accuracy of the interfacial mass transfer rate is limited by several factors，including complex interface properties，model precision，and experimental measurement accuracy. In bubbly flow systems，the significant deformability of bubble surfaces further complicates the mass transfer mechanism，making accurate prediction of the mass transfer rate difficult and posing major challenges for the development of mass transfer equipment. To address these challenges，a novel interface mass transfer algorithm based on the volume-of-fluid method is employed to rigorously simulate the free rise of a single bubble with concomitant mass transfer. The algorithm adopts a unified single-field formulation，enabling the simultaneous calculation of the local bubble volume change，and is therefore suitable for investigating single-bubble free rise behavior with mass transfer. By analyzing the simulation results，the motion behaviors of the bubbles under different Eötvös numbers (Eo) and Morton numbers(Mo)，as well as the mass transfer characteristics under different Schmidt numbers(Sc)，are obtained. The influences of bubble deformation，trajectory，and local flow field on the bubble mass transfer rate and concentration distribution are further investigated. The results indicate that the mass transfer rate and concentration distribution are closely related to the dynamic behavior of the bubble. Instabilities in bubble shape and motion path enhance gas-liquid mass transfer，while liquid-phase vortices induced by bubble motion significantly alter the solute concentration distribution in the liquid. Overall，this study provides theoretical support for an in-depth understanding of gas-liquid interfacial mass transfer mechanisms.

关键词

气液传质 / 气泡流 / 数值模拟 / 尾流 / 厄特沃什数 / 莫顿数 / 施密特数

Key words

gas-liquid mass transfer / bubble flow / numerical simulation / wake / Eo / Mo / Sc

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