不同曝气量和纵横比下针孔喷射气泡羽流摆动特性的数值模拟研究

Numerical simulation of the oscillating characterization of needle sparging bubble plume under different aeration rates and aspect ratios

该文采用三维欧拉-欧拉法结合标准k-ε紊流模型模拟了矩形鼓泡塔内针孔喷射的气泡群的瞬时流动特性,并开展了纵横比和曝气量对气泡羽流摆动特性的影响分析。数值模拟结果很好地复现了低空隙率气泡羽流的周期性运动特性。当纵横比H/W=1.0时,气泡羽流的流动形态和结构稳定;当纵横比H/W=2.25和H/W=3.0时,气泡羽流的流动形态不稳定,呈现周期性摆动规律。在模拟计算中曝气量Q_0的范围为13.3 mL/s–170.4 mL/s。随着Q_0的增加,气泡羽流摆动周期减小并且趋于稳定,液体的含气率在增加并呈线性趋势;两种纵横比对气泡羽流的摆动周期和气体总空隙率的影响较小。

A computational model based on a 3D Eulerian–Eulerian approach along with standard k- e turbulence model is used for the simulation of the transient two-phase flow in a needle sparger rectangular bubble column, and the influence of aspect ratio and aeration rate on the oscillating characteristics of bubble plume is analyzed. The calculated results reproduce well the periodic movement of the bubble plume. In case the ratio of height to width equals 1.0, the flow has an essentially stationary character in which one circulation cell spreads over the full width of the bubble column. For the aspect ratio is 2.25 and 3.0, an unsteady flow structure develops, which corresponds to the periodic movement of the bubble swarm. Gas flow rates （Q_0） ranging from 13.3 to 170.4 mL/s are used throughout the simulations. The period of oscillation rapidly reduces as Q_0 increases until reaching an approximately constant value, and the global gas hold-up shows a linear trend. The influence of two different aspect ratios on the oscillation period and the total void fraction of the bubble plume is small.