Cold Model Study of the Effects of Density Difference and Blockage Factor on Mold Powder Entrainment

Yoshida, Jin; Ohmi, Tatsuya; Iguchi, Manabu

doi:10.2355/isijinternational.45.1160

Cited by 20 publications

(14 citation statements)

References 8 publications

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“…However, during the DD, this term probably becomes negative, which joins to the sink of energy together with e, providing a total unbalance of energy (Eq. [8]). This stage is schematized hypothetically in Figure 12(b), where as seen, during DD, the flow responds with a considerable increase of turbulent and convective transport mechanisms of kinetic energy (left-hand side of Eq.…”

Section: B Two Tracer Mixing Patternsmentioning

confidence: 93%

“…This stage is schematized hypothetically in Figure 12(b), where as seen, during DD, the flow responds with a considerable increase of turbulent and convective transport mechanisms of kinetic energy (left-hand side of Eq. [8]) to compensate for transforming the production rate of kinetic energy into a negative scalar. This unbalance of energy ushers the formation of vortexes in the region located between both jets, particularly in the lower part of the mold, which makes the flow to become far from being irrotational (i.e., the vorticity has finite values in this region under these circumstances).…”

Section: B Two Tracer Mixing Patternsmentioning

confidence: 99%

“…[6] For instance, Takatani et al [7] found that the horizontal velocity under the meniscus fluctuates strongly through the width of a conventional slab mold. Using a physical model, Yoshida et al [8] identified a meniscus-descending flow along the outer surface of the SEN as a result of differential pressure in this region. This descending flow carries out flux, which, once reaching the port position, is easily entrained by the discharging jet-distributing flux particles inside the steel bulk.…”

Section: Introductionmentioning

confidence: 98%

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Cyclic Turbulent Instabilities in a Thin Slab Mold. Part I: Physical Model

Torres-Alonso

Morales

Garcia-Hernandez

et al. 2010

Metall Mater Trans B

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A water-physical model of a funnel-type thin slab mold fed by a two-port submerged entry nozzle (SEN) was employed to characterize the flow of liquid steel using dye tracer, particle image velocimetry, and video recording experiments. The overflow fluid flow pattern was the typical double-roll flow. A cyclic, low-frequency (%0.01 s À1 ), and energetic flow distortion of a short-lived (8 to 12 seconds) inducing high meniscus oscillation was identified. Its intensity grew with high casting speeds (5 and 7 m/min) and with a shallow SEN immersion position (200 mm from the meniscus level to the SEN tip). This distortion originated from the apparent existence of vortex flows located below the two discharging jets, which are formed by shear stresses in their ends that act on the surrounding fluid. These vortexes exert momentum transfer upward through a cascade mechanism from the lowest part of the discharging jets until reaching the region close to the SEN tip. This cascade momentum transfer widens the separation of both jets, enhancing the fluid velocities of the upper rolls, which promotes a high-amplitude standing wave. It is inferred, based on the experimental results, that this flow distortion originated from an instantaneous unbalance of the turbulent kinetic energy in the discharging jets. The negative production of kinetic energy is ascribed as the source of this unbalance, which is compensated by a higher contribution of the turbulent kinetic energy through mean convection and turbulent transport mechanisms manifested through higher velocities. After the restoration of the energy balance, the system yields a stable meniscus to repeat the low-frequency cycle.

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Section: B Two Tracer Mixing Patternsmentioning

confidence: 93%

Section: B Two Tracer Mixing Patternsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Cyclic Turbulent Instabilities in a Thin Slab Mold. Part I: Physical Model

Torres-Alonso

Morales

Garcia-Hernandez

et al. 2010

Metall Mater Trans B

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“…All possible mechanisms, so far reported in the open literature, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] are shown in Figs. 18(a)-18(h).…”

Section: Flux Entrainment or Entrapment Mechanismsmentioning

confidence: 99%

Control of Meniscus Stability in Medium Thickness-straight Walls Slab Mould

Gutierrez-Montiel

Morales

2013

ISIJ Int.

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Meniscus stability influenced by fluid flow patterns inside a medium thickness-parallel mould walls was analyzed using water modeling techniques including dye tracer injection, PIV and ultrasonic measurements on real time of meniscus levels. Two different submerged entry nozzles (SEN) were compared, the first is under current operation at the caster which yields a very high level of turbulence and the second is a computer aided design SEN which is aimed to reemplace the first one. The experimental results indicate that the first SEN 1 induces a single-unstable large flow roll which promotes large bath oscillations and generation of vortex flows on the bath surface. Fluid speeds at meniscus level reach magnitudes as large as 0.6 m/min and in the wall mould as high as a 0.95 m/s which are large enough to attain "shell washing conditions". Meanwhile SEN 2, new design, yields a very stable meniscus with speeds as large as 0.45 m/s at the meniscus in a stable-double flow roll. The analysis of entrapment and entrainment mechanisms of slag leads to conclude that the first SEN will induce slag entrapment under almost all operating conditions while the second SEN will induce slag entrapment only under very specific conditions of high casting speed of 3.68 m/min.

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“…6) Takatani et al 7) found that in a conventional slab mold the horizontal velocity under the meniscus fluctuates strongly. Using a physical model Yoshida et al 8) identified downward flows at the meniscus along the outer surface of the SEN due to the existence of differential pressure in this region. This descending flow carries down flux that, once reaching the port position, is easily entrained by the discharging jet into the steel bulk.…”

Section: Introductionmentioning

confidence: 99%

Design of a Submerged Entry Nozzle for Thin Slab Molds Operating at High Casting Speeds

et al. 2012

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A submerged entry nozzle (SEN) for thin slab casters operating at casting speeds as high as 7.5 m/minute was developed based on fundamental grounds of boundary-layer theory and water modeling experiments. Experimental techniques included tracer injection to observe overall fluid flow patterns, high speed video camera and image analysis to follow dynamic changes of meniscus levels and particle image velocimetry to measure water speeds in the mold. This design was compared with two other SEN designs of nozzles under current commercial use at various thin slab casters. Direct comparisons of mathematical simulations and experimental results among the three SEN's evidenced that this new SEN yields very stable flows which are independent from casting speed and nozzle immersion depth. Fluid flow developed by this SEN consists of a double roll pattern without generation of superficial vortices. The two other SEN's yield instable discharging jets due to and excessive shearing effects with the surrounding fluid inducing severe dissipation of kinetic energy which promotes severe tailing effects inducing strong meniscus oscillations. The proposed design has reported good industrial performances and a longer operating life because the slag protection belt suffers less wear thanks to smaller velocities of the bath in contact with the SEN wall.

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Cold Model Study of the Effects of Density Difference and Blockage Factor on Mold Powder Entrainment

Cited by 20 publications

References 8 publications

Cyclic Turbulent Instabilities in a Thin Slab Mold. Part I: Physical Model

Cyclic Turbulent Instabilities in a Thin Slab Mold. Part I: Physical Model

Control of Meniscus Stability in Medium Thickness-straight Walls Slab Mould

Design of a Submerged Entry Nozzle for Thin Slab Molds Operating at High Casting Speeds

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