颗粒物性对水平气力输送管中颗粒浓度分布影响的数值模拟

Numerical study of effect of particle properties on particle phase volume fraction in a horizontal pneumatic conveying pipe

在考虑气-固流体的双向耦合、颗粒与颗粒的碰撞、颗粒与壁面的碰撞以及滑移摩擦的基础上,对气体相湍动能采用修正的k-ε二方程模型,颗粒相湍动动能采用颗粒动力学方法,发展建立了水平气力输送的数学模型和相应的计算方法,数值研究了颗粒粒径和密度对悬浮颗粒的浓度分布的影响。结果发现在水平气力输送中,在颗粒湍动、颗粒自身重力、颗粒与颗粒的碰撞以及颗粒与壁面的碰撞的共同作用下,颗粒浓度分布不均匀,其垂向分布存在着两种不同的形态。颗粒粒径越小、密度越低,越容易出现Ⅰ型分布:即颗粒浓度呈现出从管底部到管上部会先由小变大,到某位置时达最大值,尔后又向小变化的趋势。

Taking the interaction between fluid and particles, collision between particles, and collision and fraction between particles and wall into account, a locally averaged three-dimensional gas-particle two-fluid flow model for horizontal pneumatic conveying pipe was built up based on the modified k-ε model for gas phase and the kinetic theory for granular flow, and the relevant numerical algorithm and computational code were developed consequently. The model makes it possible to calculate the macroscopic behaviors such as effective pressure, effective viscosity and shear viscosity of particle phase. The effects of particle diameter and particle density on the distribution of particle phase volume fraction are numerically studied. The results show there are two types of vertical distribution of partic(?)e phase volume fraction in horizontal conveying, in which the type Ⅰ distribution, where from bottom wall to top wall of the pipe, the particle phase volume fraction increases firstly, achieves a maximum value at a certain position and then decreases, usually appears when the particle diameter is relatively small and the density is relatively low.