Use of electromagnetic induction tomography for monitoring liquid metal/gas flow regimes on a model of an industrial steel caster

Abstract

Monitoring of the steel flow through the submerged entry nozzle (SEN) during continuous casting presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould. Electromagnetic inductance tomography (EMT) presents an attractive tool to visualize the steel flow profile within the SEN. In this paper, we investigate various flow regimes over a range of stopper positions and gas volume flow rates on a model of a submerged entry nozzle. A scaled (approximately 10:1) experimental rig consisting of a tundish, stopper rod, nozzle and mould was used. Argon gas was injected through the centre of the stopper rod and the behaviour of the two-phase GaInSn/argon flow was studied. The experiments were performed with GaInSn as an analogue for liquid steel, because it has similar conductive properties as molten steel and allows measurements at room temperature. The electromagnetic system used in our experiments to monitor the behaviour of the two-phase GaInSn/argon flow consisted of an array of eight equally spaced induction coils arranged around the object, a data acquisition system and a host computer. The present system operates with a sinusoidal excitation waveform with a frequency of 40 kHz and the system has a capture rate of 40 frames per second. The results show the ability of the system to distinguish the different flow regimes and to detect the individual bubbles. Sample tomographic images given in the paper clearly illustrate the different flow regimes.

Magnetic flux distortion in two-phase liquid metal flow: Model experiment

“…2 However, experiments point out that the magnetic flux is strongly perturbed by a diluted bubbly flow and cannot be modeled by the Maxwell approach. 3,4 This result has been confirmed by numerical simulations. 5 Using the reciprocity theorem and an expansion of magnetic vector potential, Bowler et al have estimated the perturbation in impedance due to a single small defect in a conducting medium.…”

DRESDYN -- a new facility for MHD experiments with liquid sodium

“…Starting with very small experiments at a flat wall, we plan to go over later to boiling experiments at rods or rod bundles. For the visualization of the boiling we plan to use the Mutual Inductance Tomography [43], as well as X-ray radiography [44] and, in collaboration with another group at HZDR, the ultrafast X-ray tomography [45].…”

Combined Electromagnetic Tomography for Determining Two-phase Flow Characteristics in the Submerged Entry Nozzle and in the Mold of a Continuous Casting Model

“…This produces a total of 28 independent mutual inductance values that are used to reconstruct the metal distribution in the SEN. More details on the application of this method for the detection of large and small argon bubbles in Mini-LIMMCAST can be found in recent publications. [14,15] The CIFT technique relies on the fact that, by exposing the flow of a highly conducting melt to an externally applied magnetic field, electrical currents are induced that give rise to a perturbation of the applied field. This flow-induced field perturbation, which is measurable outside the fluid volume, contains information about the flow structure and can be exploited to reconstruct the velocity field.…”

“…At the same facility, the corresponding two-phase aspects of the flow in the SEN have been separately studied by MIT. [14,15] In this study, we go one step further by exploiting the synergies between MIT and CIFT to obtain a better understanding of some typical two-phase flow features as they occur in the continuous casting process. We start with a short description of the Mini-LIMMCAST facility at HZDR, and we briefly recall the principles of both the MIT and the CIFT method.…”