关键词: 鼓泡塔, 气液两相流, 计算流体力学, 气泡群曳力模型, 径向力平衡模型, 壁面润滑力模型

Abstract:

The commercial bubble column reactors are normally operated under the conditions of pressurized state and churn turbulent bubbly flow which the superficial gas velocity always exceeded 0.1 m·s^-1.However, most of the published literatures are focus on the cold model experimental investigation of the flow field characteristics in pressurized churn-turbulent bubble columns, and the empirical or semi-empirical correlations which were on the basis of the cold model experimental data to quantitatively estimate the characteristic parameters.Therefore, it is lack of the systematic study on the flow characteristics in the pressurized turbulent bubble columns by the hydrodynamic models with interactions between bubbles and liquid phase.In this work, a steady 2-D axisymmetric hydrodynamic two-fluid model of pressurized bubble column was developed on the platform of FLUENT 15.0 with the UDF sub-models which described the bubble swarm interface forces.The numerical investigations upon the flow field characteristics of pressurized churn turbulent bubble column with the operation pressure varying from 0.5 MPa to 2.0 MPa, and superficial gas velocity from 0.2 m·s^-1 to 0.31 m·s^-1 were performed.Moreover, the comparisons between the simulation results and cold model experimental data were implemented.The comparisons indicated that, the model with the bubble swarm interface forces including improved bubble swarm drag force model, lateral force balance model, and wall lubrication force model, is able to reflect the influences of operation pressure and superficial gas velocity upon flow pattern, that is, the elevating operation pressure leads to increase of time averaged gas holdup and decrease of time averaged axial gas phase velocity, whereas for the ascending superficial gas velocity, the gas holdup and gas phase velocity are both raising.Consequently this mathematical model could correctly predict the basic gas-liquid flow pattern in the turbulent pressurized bubble columns, and simulation results are in good agreement with the experimental data.

Key words: bubble column, gas-liquid flow, computational fluid dynamics, bubble swarm drag force model, lateral-force balance model, wall lubrication force model