进口边界条件对边壁进风鼓泡床流动的影响研究

Influence of Inlet Boundary Condition on Flow Field of Bubbling Fluidized Bed with Orifice near the Wall

为了探寻速度进口边界条件对边壁进风鼓泡流化床床内气泡行为的影响,根据欧拉-欧拉双流体模型,应用标准kε-方程模型处理气体湍流流动,分别采用均匀进风速度边界条件、脉动项按正态分布和脉动项按正弦分布的脉动进风速度边界条件,对鼓泡床内的气固两相流动过程进行了数值模拟.结果表明:采用脉动进风速度边界条件时,在非射流孔道处气体可形成气泡,气泡的上升速度比匀速进风时小;气体能够充分地与固体颗粒相互作用,床层中的空隙率主频较小;在设置边界条件时考虑脉动能够更合理地预测和分析床内气泡的尺寸、速度等特性.

In order to study the influence of velocity inlet boundary condition on the bubble behavior in a bubbling fluidized bed with orifice near the wall,numerical simulation has been performed to the gas-solid two-phase flow in the bed using Euler-Euler two-fluid model and standard k-ε equation under steady velocity inlet boundary conditions as well as turbulent velocity inlet boundary conditions respectively with normal and SIN distribution items.Results show that under turbulent inlet boundary conditions,bubbles may form in other areas except for the orifice,and the rising speed of bubbles will be slower than that under steady conditions.Under turbulent conditions,the gas mixes with solid particles adequately,and the dominant frequency of voidage signals is relatively smaller.For reasonable prediction of the bubble size and velocity,it is recommended to consider the turbulent factors when setting relevant boundary conditions.