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过程工程学报 ›› 2019, Vol. 19 ›› Issue (2): 279-288.DOI: 10.12034/j.issn.1009-606X.218230

• 流动与传递 • 上一篇    下一篇

颗粒团聚对稀相气固流动脉动关联项的影响

冯 蘅1, 李清海1*, 蒙爱红1, 张衍国1, 孔 博2   

  1. 1. 清华大学热科学与动力工程教育部重点实验室,二氧化碳资源化利用与减排技术北京市重点实验室,清华大学?滑铁卢大学微纳米能源环境联合研究中心,清华大学能源与动力工程系,北京 100084 2. 美国能源部艾姆斯实验室, 美国 IA 50011-2230
  • 收稿日期:2018-06-25 修回日期:2018-08-29 出版日期:2019-04-22 发布日期:2019-04-18
  • 通讯作者: 李清海 liqh@tsinghua.edu.cn
  • 基金资助:
    国家自然科学基金资助项目 (U1302274)

Effects of particle clusters on fluctuation coupling terms in dilute gas-particle turbulent flows

Heng FENG1, Qinghai LI1*, Aihong MENG1, Yanguo ZHANG1, Bo KONG2   

  1. 1. 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 2. Ames Laboratory-USDOE, Ames, IA 50011-2230, USA
  • Received:2018-06-25 Revised:2018-08-29 Online:2019-04-22 Published:2019-04-18
  • Contact: Qing HaiLi liqh@tsinghua.edu.cn
  • Supported by:
    Projects (U1302274) supported by the National Science Foundation of China

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。

关键词: 两相流, 数值模拟, 动力学理论, 颗粒团聚, 脉动关联项

Abstract: 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 by Bhatnagar?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 and drift velocity were identified.

Key words: two-phase flow, numerical simulation, kinetic theory, particle cluster, fluctuation coupling term