考虑颗粒旋转的颗粒动力学模拟提升管气固两相流动特性

Numerical Study on Gas-Solid Flow in a Riser Using Dynamic Theory with Consideration of Particle Rotation

流化床内颗粒旋转会影响颗粒相的流动特性,目前在流化床数值模拟中普遍采用的颗粒动力学模型却没有考虑颗粒的旋转效应。今运用基于颗粒动力学理论的欧拉-欧拉气固多相流模型,考虑颗粒旋转流动对颗粒碰撞能量交换和耗散的影响,提出了考虑颗粒旋转效应的颗粒动力学模型以及颗粒相守恒方程,数值模拟提升管内气体颗粒两相流动特性。计算结果表明提升管内中心区域为低浓度-高速的颗粒上升流动、壁面区域为高浓度-低速的颗粒下降流动。分析了颗粒粗糙度系数对颗粒相能量耗散、颗粒平动温度和黏度的影响。随着颗粒粗糙度系数的增加,颗粒碰撞能量耗散先逐渐增加后减小。颗粒平动温度和黏度的变化趋势是相反的,表明颗粒旋转产生摩擦将导致颗粒旋转脉动能量的改变,影响提升管内气体-颗粒两相宏观流动特性。

In the gas-particle two-phase,although the particle rotation will influence the hydrodynamics of the particle phase in the fluidized bed,the particle rotation effect has not been considered generally in the dynamic theory of granular flow.In this study,using a two-fluid model combining with the dynamic theory of granular flow,the numerical analyses on the effect of the particle rotation on gas-particle two-phase flow behavior in a fluidizing riser were conducted.Via the roughness coefficient,the energy dissipation due to the particle rotation was taken into account in the model,and a new dynamic theory of granular flow considering the effect of particle rotation and the conservation equation for the particles were developed.Numerical results show that the obvious core-annulus flow structure was observed,which has an upward flow with high velocity and low concentration in the core region and a low velocity and high concentration downward flow near the wall of the riser.With changing the roughness coefficient from-1 to 1,the energy dissipation of the particles increases at first and then decreases gradually.The translational granular temperature and the viscosity of the particles show an opposite trend,which indicates the friction due to the particle rotation has a significant effect on the change of the particle rotation fluctuation energy.