Recent developments on the contactless inductive flow tomography


Recent developments on the contactless inductive flow tomography

Wondrak, T.; Ratajczak, M.; Stefani, F.; Gundrum, T.; Timmel, K.; Pal, J.; Eckert, S.

The Contactless Inductive Flow Tomography (CIFT) allows the reconstruction of the mean three dimensional flow structure in conducting liquids [1]. Exposing the liquid to one or multiple applied magnetic fields and measuring the flow induced magnetic field around the fluid volume, it is possible to infer the velocity field by solving a linear inverse problem with appropriate regularization techniques. One challenge is the reliable detection of the tiny flow induced perturbation of the applied magnetic field. Typically, the flow induced magnetic field is about 3 to 5 orders of magnitude smaller than the applied magnetic field, so that a measurement system with a high dynamic range is required.
We start with a short overview of the first demonstration experiment of CIFT [1]. In a cylindrical vessel filled with GaInSn a propeller generates a three dimensional flow structure with a maximum velocity of 1 m/s. The flow induced magnetic field is about 3 orders of magnitude smaller than the applied magnetic field.
One promising application for CIFT is the continuous casting of steel in which the flow structure in the mould is very important for the quality of the produced steel. For a model of a continuous slab caster operated with GaInSn we developed a measurement system consisting of one excitation coil around the mould and 14 magnetic field sensors [2]. In this industrially relevant setup the flow induced magnetic field is about 4 orders of magnitude smaller than the applied magnetic field. We were able to reconstruct different flow transitions in the mould in case that Argon was injected into the submerged entry nozzle (SEN) [3], and various effects of an electromagnetic stirrer at the SEN on the flow in the mould [3]. Recent developments concerned the reconstruction of the flow in the mould in the presence of a strong static magnetic field. Additionally, we show preliminary measurements at a modified Rayleigh-Bénard setup operated with GaInSn demonstrating the applicability of CIFT for thermally driven convection systems with velocities in the order of 0.01 m/s. Typical features of the thermally driven turbulent flow could be detected in the magnetic field measurements and were verified by simultaneous temperature measurements recorded by small thermocouples.

References
1. F. Stefani et al., Physical Review E, 70 (2004), 056306
2. T. Wondrak et al., Measurement Science & Technology 21 (2010), 045402
3. T. Wondrak et al., Metallurgical and Materials Transactions B 42 (2011), 1201-1210

Keywords: contactless inductive flow tomography; liquid metal; flow measurement; continuous casting

  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.4.2015, Dresden, Germany

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Publ.-Id: 22927