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论文类型：期刊论文

发表时间：2011-10-01

发表刊物：INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW

收录刊物：EI、Scopus、SCIE

卷号：32

期号：5

页面范围：1057-1067

ISSN号：0142-727X

关键字：Bubble; Metallic melt; Number density function; Break-up; Coalescence

摘要：This paper reports on progress in developing CFD simulations of gas bubble-metallic melt turbulent flows induced by a pitched-blade impeller with an inclined shaft. Foaming process of aluminum foams, in which air is injected into molten aluminum composites and the melt is mechanical stirred by the impeller, has been investigated. A two-fluid model, incorporated with the Multiple Reference Frames (MRF) method is used to predict the three-dimensional gas-liquid flow in the foaming tank, in which a stirring shaft is positioned inclined into the melt. Locally average bubble size is also predicted by additively solving a transport equation for the bubble number density function, which accounts for effects of bubble breakup and coalescence phenomena. The computed bubble sizes are compared with experimental data from our water model measurement and reasonable agreements are obtained. Further, simulated results show that the volume averaged total and local gas fractions are generally increased with rising impeller speed and gas flow rate. The local averaged bubble size increases with increasing gas flow rate and orifice diameter and decreasing liquid viscosity, and decreases also with rising rotation speed of the impeller. (C) 2011 Elsevier Inc. All rights reserved.