Fluid Flow and Mixing in a Six Strand Billet Caster Tundish: A Parametric Study.

Abstract

Mixing phenomena in a six strand billet caster tundish has been studied by numerically solving the Navier Stokes equations along with the species concentration equation in a boundary fitted coordinate system comprising the geometry of the tundish. The solution of the species concentration equation has been utilized to compute the mix, dead and plug volume of the tundish under different flow conditions. The numerical procedure and solution algorithm has been first verified by comparing the numerically obtained residence time distribution curve, which agree well with that of the experiments done for a single strand bare tundish by Singh and Koria. 44) It has been observed that the ratio of the mix to dead volume for the six strand tundish has a maximum value for a particular position of the outlets. At that particular position of the outlets (where mixing is best), an APB is placed on the bottom of the tundish surrounding the incoming inlet jet and the height of the APB has been varied to see the effect on mixing in the tundish. It has been observed that the ratio of mix to dead volume further increases with the use of APB and attains a peak value after which it decreases with the increase of the height of the APB signifying the existence of an optimum APB height. At this optimum height of the APB, the shroud immersion depth was made to change from 0 to 400 mm. It was also observed that there exists an optimum immersion depth of the shroud where the ratio of mix to dead volume still attains another peak signifying still better mixing. However, increasing the immersion depth to higher values spoils mixing significantly.KEY WORDS: billet caster tundish; mixing; mean residence time; advance pouring box; shroud immersion depth.benefit in terms of gaining better mixing in the tundish as discussed in Sec. 3.2 rather than putting dams and weirs. It should be noted here that fixing up dams and weirs in a tundish is a much involved job rather than changing outlet positions, which seem to be rather easier. Moreover on the leeward side of the dams and weirs, there will normally be dead zones which rather spoils mixing in the tundish. So this has been tried in the present work and in addition to this an Advanced Pouring Box (APB) has been put around the inlet jet where it impinges on the bottom plane so that the resulting flow may create better mixing in the tundish. The effect of the height of the APB brings in interesting variations to the flow field and also to the mixing in general. The effect of the shroud immersion depth makes the flow field still benign to mixing, which is normally not found in literature in the present form. So the present study is an effort in this direction. Physical Description of the ProblemThe geometry of the billet caster tundish is shown in Fig. 1a along with the three outlets. The tundish is shown half because of the symmetry about the inlet plane. The depth of the tundish and the bottom pad are 572 and 280 mm respectively with the size of the inlet as 25 mmϫ50 mm and all other dimensions a...

Fluid Flow Characterization in Asymmetric Tundish

“…The dead volume is the fluid that moves slowly in the tundish and stays for longer than double 1,[6][7][8] (used in this paper) or 2.5 times 3,4,10,12) the mean residence time. F curve can be used to reflect the residence time distribution of new and old molten steel in tundishes.…”

“…However, if the combined model is used to calculate the RTD curves of different outlets, there may exist negative volume fraction of dead region or bigger calculation errors. 13) In addition, researchers 4,6,7,[9][10][11][12] tended to consider the tundishes were symmetric and only measured the concentration variation of half outlet when they studied the dead region of multistrand tundishes. The dead volume fracion obtained by this method is different from that of single-strand tundish in physical meaning.…”

“…Then C curve was analyzed or translated into E curve. Many researchers 4,6,7,9) used the combined model for single-strand tundishes to calculate the volume fractions of dead region, plug flow and well-mixed flow of different strands. They evaluated the flow characteristics of tundishes by comparing the volume fraction difference between different strands before and after optimization.…”

“…RTD curve analysis models for multi-strand tundishes were mainly worked out on the basis of the combined model. [3][4][5][6][7][8][9][10][11][12] Pulse stimulus-response method was often adopted to obtain the outlet tracer concentration versus time curve (C curve) in simulation experiment of multi-strand tundishes. Then C curve was analyzed or translated into E curve.…”

Numerical and physical modelling of tundish slag entrainment in the steelmaking process

“…These studies were aimed at improving the flow characteristics in the tundish (Chattopadhyay, Isac, and Guthri, 2010;Cloete, 2014;Jha, Dash, and Kumar, 2001;Jha, Rao, and Dewan, 2008;Kumar, Koria, and Mazumdar, 2007;Kumar, Mazumdar, and Koria, 2008;Mazumdar and Guthri, 1999;Sahai and Emi, 1996;Sahai and Burval, 1992; Tripathi and Ajmani, 2011). These studies have led to the use of flow control devices (FCDs) to increase the melt residence time in the tundish and provide surface-directed flow so as to assist with inclusion removal.…”