摘要
研究了颗粒团聚对描述稀相气固两相流的气固相宏观控制方程中待封闭气固脉动关联项的影响规律并建立关键待封闭项代数模型。根据气相速度脉动与固相浓度关联项(漂移速度)控制方程,将漂移速度表达为固相非均匀程度和气固平均滑移速度的代数模型。分别采用两种基于颗粒动理学的欧拉-欧拉框架介尺度方法模拟三维周期条件且固相平均浓度为1%的稀相气固两相流动,第1种方法假设固相速度分布函数f为各项同性的双流体方法(TFM);第2种方法假设f服从各向异性高斯分布的积分矩法(AG)。网格分辨率为颗粒直径dp的1.75倍,气固间动量交换采用Stokes曳力模型,并与文献中采用相同参数设置的欧拉-拉格朗日(E-L)方法模拟结果进行对比。结果表明,AG方法的准确度优于TFM方法,气固平均滑移速度、气固脉动能等更接近E-L方法模拟结果。颗粒聚团的积分尺度小于气相脉动速度的积分尺度,两者均呈各向异性,竖直分量高于水平分量。模拟得到了气固速度脉动关联系数和漂移速度系数。
The effect of particle clusters on gas-solids fluctuation coupling terms in Reynolds stresses transport equations was investigated in this work.Based on its transport equation,covariance of solids phase volume fraction and gas phase fluctuating velocity,namely drift velocity was closured by an algebraic model,which was a function of both degree of segregation and mean slip velocity.Thereby two different kinetic-based Euler-Euler mesoscale methods were applied to simulate a dilute gas-particle flow in a triple periodic domain where solids phase averaged volume fraction was 1%.Stokes drag law was applied for inter-phase momentum transfer.Inter-particle collisions were approximated byBhatnagar-Gross-Krook model.Mesh resolution in this study was as 1.75 times as particle diameter dp.The difference between these two approaches was the way to solve solids phase kinetic equation.The first approach was an Anisotropic Gaussian(AG)Quadrature based moment method of which particle phase velocity density function f was assumed to follow a multivariate anisotropic Gaussian.The second approach was a typical two-fluid model(TFM)of which assumed f to follow isotropic distribution.To validate these two methods,results were compared with results given by a Euler-Lagrange(E-L)method in the literature.It demonstrated that AG method was able to produce better comparable results than TFM.For instance,the flow field properties given by AG method were closer to results given by E-L method,including mean slip velocity,gas and solids phase turbulent kinetic energy.Results showed that the integral scale of particle clusters was smaller than that of gas-phase fluctuation velocities.And the integral scale of both particle clusters and gas-phase fluctuation velocities turned out to be anisotropic that vertical components were larger than lateral components.The falling of particle clusters was mainly suppressed by form drag(i.e.gas pressure between front and tail).In the end,the coefficients of both gas-solids fluctuation velocity covariance an
作者
冯蘅
李清海
蒙爱红
张衍国
孔博
Heng FENG;Qinghai LI;Aihong MENG;Yanguo ZHANG;Bo KONG(Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Beijing Key Laboratory for CO2 Utilization and Reduction Technology,Tsinghua University-University of Waterloo Joint Research Center for Micro/Nano Energy&Environment Technology,Department of Energy and Power Engineering,Tsinghua University,Beijing 100084,China;Ames Laboratory-USDOE,Ames,IA 50011-2230,USA)
出处
《过程工程学报》
CAS
CSCD
北大核心
2019年第2期279-288,共10页
The Chinese Journal of Process Engineering
基金
国家自然科学基金资助项目(编号:91434119)
关键词
两相流
数值模拟
动力学理论
颗粒团聚
脉动关联项
two-phase flow
numerical simulation
kinetic theory
particle cluster
fluctuation coupling term
