Experimental study of a bubble-driven liquid metal two-phase flow under the influence of AC magnetic fields

Bubble-driven flows are used in many industrial facilities. In metallurgical applications, gas bubbles are injected into furnaces, ladles, or similar melt containing transfer vessels in order to homogenize the melt and their physi-cal and chemical properties. The principle is that a bubble plume accelerates the surrounding liquid upward and produces a recirculation zone. This method is used for steelmaking in bottom blown reactors, and the hydrodynamics of such gasstirred melts were studied in depth by Sahai and Guthrie,[1,2] Johansen et al.,[3] and Mazumdar et al.[4]
The efficiency of gas-stirred systems can be discussed in terms of mixing time, input energy rate, mixing vessel shape, or the type and location of the gas injection. The high relevance of liquid metal stirring makes it worth-while to search for possible improvements of such a pro-cess. A mixing enhancement could yield a better material quality, a reduction of the mixing time, and therefore result in lower mixing gas consumption or lower electric power consumption.
In general, the application of AC magnetic fields can be used to force a motion inside conducting liquids such as liquid metal. Therefore, the overall efficiency of gas-stirred liquid metal systems may be improved by the ap-plication of customized AC-magnetic fields. In this paper, an experimental study is presented considering the influ-ence of different AC magnetic fields on a bubble-driven flow of a liquid metal. The investigation is focused on the bubble distribution and the liquid circulation inside a liq-uid metal column driven by a central jet produced by gas injection. The fluid vessel has a circular cross-section and electrically insulating walls. Low gas flow rates were applied, resulting in a plume of separated bubbles rising inside a spot around the cylinder axis.