Abstract:

The gas-solid flow in gas-solid bubbling fluidized bed was simulated by a combined approach of computational fluid dynamics (CFD) and the two fluid model (TFM), based on the modified EMMS drag model. A new image processing method derived from image calibration was applied to study bubble characteristics with focus on overall and radial distributions of bubbles as well as bubble profiles in terms of averaged equivalent diameter, rising velocity, degree of sphericity, and bubble lifetime at various superficial gas velocity. The results showed that smaller bubbles most located at the bottom of beds and wall region whereas larger bubbles most located at the central region of beds. With increase of superficial gas velocity, the bed height were gradually increased and bubble profiles of the averaged equivalent diameter, the frequency of occurrence, the rising velocity and the lifetime were all increased except that the degree of sphericity was decreased. Nevertheless, once the superficial gas velocity increased to a certain level, its increase would no longer have any significant impact on the rising velocity.

Key words: gas-solid bubbling fluidized bed, multiphase flow, computational fluid dynamics, TFM, EMMS, bubble

摘要：

基于EMMS曳力模型，采用双流体的方法对气固鼓泡床内的气固流动特性进行模拟，建立基于图像处理气泡特性的分析方法，重点研究了不同表观气速下气泡在床层内分布特性，包括气泡平均当量直径、气泡速度和气泡球形度的轴向分布，以及气泡的生命周期。研究结果表明，小气泡多集中在床层底部和壁面区域，而大气泡多集中在床层中间区域。随着表观气速的增加，床层高度不断增加，气泡的球形度降低，气泡的大小、出现频率、上升速度以及生命周期均增加；然而，当表观气速增大到一定程度，继续增加气速对气泡的上升速度影响不大。

关键词: 气固鼓泡床, 多相流, 计算流体力学, TFM, EMMS, 气泡