Calculation Accuracy and Efficiency of a Transient Model for Submerged Entry Nozzle Clogging
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NOZZLE clogging describes a phenomenon of the blockage of the flow passage, which is due to a gradual buildup of solid materials on the nozzle wall. This buildup of solid materials would disturb the fluid flow in the passage before the blockage. During the continuous casting of steel, clogging of the submerged entry nozzle (SEN) is a long-term problem leading to undesired issues or even process disruptions. Possible clogging mechanisms are categorized in Table I. Among these possible mechanisms, the first one, i.e., attachment of the nonmetallic inclusions (NMIs) on the SEN wall, is considered the major mechanism.[1] Further discussions are presented in Section IV–C. Recently, the current authors developed a transient model for nozzle clogging based on an Eulerian–Lagrangian approach.[25] Key features of the model are summarized as follows.
H. BARATI is with the Chair for Modeling and Simulation of Metallurgical Processes, Department of Metallurgy, Montanuniversitaet, Franz-Josef Street 18, 8700 Leoben, Austria, and also with the K1-MET, Franz-Josef Street 18, 8700 Leoben, Austria. M. WU, A. KHARICHA, and A. LUDWIG are with the Chair for Modeling and Simulation of Metallurgical Processes, Department of Metallurgy, Montanuniversitaet. Contact e-mail: [email protected] Manuscript submitted July 4, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
(1) The clogging process is divided into three steps: (a) transport of particles by turbulent fluid flow toward the wall, (b) interactions between the fluid and the wall and adhesion mechanism of the particle on the wall, and (c) formation and growth of the clog by the particle deposition on the clog front and the flow-clog interactions. (2) Two different methods are used to track the particle motion: in the near-wall region using a special stochastic model[26] for wall-bounded turbulent flow and in the bulk turbulent flow using the standard random walk model. (3) The early stage of clogging, i.e., the deposition of NMI particles on the SEN wall to build up the initial layers of the clog, is treated as an enhancement of the SEN wall roughness, which, in turn, influences the turbulence boundary layer. (4) An algorithm is implemented to track the clog growth, i.e., the continuous buildup of the solid materials due to further deposition of NMI particles on the clog front. The clog region is treated as a porous medium, which interacts with the fluid flow. Preliminarily, the model was evaluated against a laboratory experiment (Figure 1).[25] In the laboratory device, which was used for investigation of clogging,[5,27] steel is melted in an induction furnace and deoxidized with aluminum to form solid alumina inclusions. After a certain holding time for deoxidation, the circular nozzle, situated at the bottom of the furnace, is opened and the molten steel flows through the nozzle, as shown in Figure 1(a). The nozzle is heated to prevent solidification
in the nozzle. After a while, the nozzle may be clogged due to the buildup of the alumina inclusion on the nozzle wall. The ma
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