基于OpenFOAM模拟精馏塔板的气液流动

Gas-liquid flow simulation of a distillation tray based on OpenFOAM

本研究对筛孔型精馏塔板上的空气-水两相流进行了模拟,模拟方法采用基于开源软件平台OpenFOAM的双流体模型框架。模拟体系选用Solari-Bell经典实验体系,研究了不同操作条件下的气液两相流动参数,包括清液层高度、气相速度、液相速度和塔板压降等,模拟结果与实验结果的变化趋势基本一致。基于CFD模拟结果,分析了不同工况下塔内气液两相速度场与气含率分布等流动参数,结果表明本工作可以较好地捕捉塔板上的气液流动特征。进一步地,讨论了应用OpenFOAM模拟精馏塔内气液两相流动的若干影响因素,在此基础上分析了气液错流体系相间曳力对模拟结果的影响,实现了与使用商业软件模拟结果相接近的预测效果,验证了使用OpenFOAM模拟精馏塔体系的可行性。

Distillation column with sieve tray is an important separation equipment and widely used in the process industry.The complex behavior of the gas-liquid two-phase flow in distillation columns,especially on the tray,significantly affects the separation performance.With increasing applications of the CFD simulation in multiphase flow,it is interesting to adopt the CFD tools in distillation design and optimization.Traditionally,commercial CFD software has been applied in this field,while they face the problems of black-box feature,limited and expensive license,inflexibility of developing tailored models,etc.Therefore,this work turns to the open source platform of OpenFOAM.By using the Eulerian solver in OpenFOAM,an experimental sieve tray column is studied.The two-phase flow characteristics under different operating conditions are explored,including the height of the clear liquid layer,the gas and liquid velocity,the pressure drop,etc.The predicted trends are consistent with the experimental results.The simulated clear liquid height decreases with increasing gas flow rate and increases with liquid flow rate,and its deviation from the experiments is attributed to the empirical drag correlations which need further study.The influences of sieve holes and liquid inlet conditions on the liquid velocity distribution have been studied.It is found that the number of sieve holes has little impact,and simulations with non-uniform liquid inlet conditions agree with the experiments better.This study verifies the feasibility of using OpenFOAM to simulate distillation columns.The next step is to apply the mesoscale approach to gas-liquid crossing flow systems,construct a new interphase drag model to improve the accuracy of the simulation,and consider the influence of heat and mass transfer on the flow field.This work lays a foundation for the next-step coupling simulations,which is promising for the design and optimization of distillation columns.