Computer analysis of molten steel flow and application to design of nozzles for continuous casting system (original) (raw)
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Bulletin of the JSME Journal of Advanced Mechanical Design, Systems, and Manufacturing , 2018
In steel continuous casting system, tundish upper nozzle has an important role on the flow rate control of the molten steel and the elimination of the inclusions and etc. Based on the basic principle of hydrodynamics, the optimal nozzle bore profile was determined with aiming to suppress the turbulence with high kinetic energy generated in the flow of the molten steel. A simulation by flow analysis and a water model experiment were performed and clarified that the turbulence with high kinetic energy could be minimized in the nozzle with newly devised inner bore profile. The actual nozzle devised was manufactured and tested in the steel works with satisfying results. It can contribute to not only improve the durability of the refractories as materials of the nozzle but also stabilize the casting operation by preventing from clogging of the nozzle.
Bulletin of the JSME Journal of Advanced Mechanical Design, Systems, and Manufacturing, 2018
A new geometrical design of the port in the flow line direction to minimize the maximum port velocity (MPV) has been proposed through the analysis using computational fluid dynamics (CFD) and water model experiments to keep uniform velocity distribution of the molten steel flow throughout the outlet of ports for submerged entry nozzle (SEN) in the continuous casting system. The adhesion of the alumina inclusions to the port part of the SEN is reduced by lowering the turbulent kinetic energy since the energy loss is minimized at the part. Both stability in the operation and quality of the steels have been brought by the present development.
Anchor-Shaped Design of a Submerged Entry Nozzle for the Continuous Casting of Steel
Open Journal of Applied Sciences, 2016
An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab continuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carried out using the Computational Fluid Dynamics technique. The performance of the proposed nozzle is numerically compared with that of a conventional cylindrical nozzle. Computer results show that the chance of formation of Karman's vortexes and powder entrapment becomes small for the anchor-shaped SEN.
Measurements of clog deposit thickness on the interior surfaces of a commercial continuous casting nozzle are compared with computational fluid dynamics (CFD) predictions of melt flow patterns and particle–wall interactions to identify the mechanisms of nozzle clogging. A submerged entry nozzle received from industry was encased in epoxy and carefully sectioned to allow measurement of the deposit thickness on the internal surfaces of the nozzle. CFD simulations of melt flow patterns and particle behavior inside the nozzle were performed by combining the Eulerian-Lagrangian approach and detached eddy simulation turbulent model, matching the geometry and operating conditions of the industrial test. The CFD results indicated that convergent areas of the interior cross section of the nozzle increased the velocity and turbulence of the flowing steel inside the nozzle and decreased the clog deposit thickness locally in these areas. CFD simulations also predicted a higher rate of attachment of particles in the divergent area between two convergent sections of the nozzle, which matched the observations made in the industrial nozzle measurements.
NUMERICAL ANALYSIS OF THE TURBULENCE EFFECTS IN CASTING MOLD DUE TO SUBMERGED ENTRY NOZZLE
In recent times, continuous casting steel products are widely used. As molten steel flows through submerged entry nozzle into casting mold is turbulent in nature. Turbulent flow as well as breaking of surface wave with entrainment of slag into the mold controls the quality of the final product. So decreasing of turbulence effect within the mold is essential. So the present numerical simulation using finite volume method with interface capturing scheme are used to predict the behaviour of interfacial fluctuation as well as the effect of turbulence within the mold by taking water model. Instead of steel and argon, water and air flow through submerged entry nozzle (SEN) in to the mold. The behaviour of water and air is similar with steel and argon by taking similarity criteria. The present two dimensional numerical investigation indicates that with increasing water velocity and decreasing mold width increase interfacial fluctuation, surface velocity, turbulence level and turbulent kinetic energy and hence controls the quality of the final product.
Some Design Aspects On Submerged Entry Nozzle In Thin Slab Casting Process
New SEN design was developed for improving steel quality and/or increase caster productivity for thin slab caster in an industrial operating plant. The new design has two main advantages; first is to reduce turbulence under meniscus to ensure cleaner product that avoid flux/slag entrapment, while the second is the ability to increase the casting speed (productivity) with higher product quality. Submerged Entry Nozzle (SEN) has two main functions; first is to prevent molten steel from re-oxidization during its transfer from tundish to mold, and second is to generate proper flow pattern inside the mold. It is evident that, steel flow control inside the mold of thin slab caster is mainly related to the design of SEN. Two finite element models are developed for quantitative and/or qualitative comparison between the new design and SEN design currently in use. The first model considers the SEN internal flow while the second is focused on the mold zone. The comparative study showed the gained superior performance when SEN port angled downward by 20° over the vertical one (0°). Furthermore, addition of small third downward port, to the main two sided ports enhanced the SEN performance through increasing the SEN depth, and mold width.
2013
In order to improve the fluid flow patterns inside the mold, a better understanding of the backflow phenomenon and its controlling parameters is necessary; then a mathematical simulation of the fluidynamics in the mold and the submerge entry nozzle (SEN) are carried out considering two typical nozzle designs and different modifications applied to the outlet ports. The numerical model considers isothermal three dimensional continuity and the Navier-Stokes equations in Cartesian co-ordinates, which are solved together with the k-ε standard turbulence and the Volume of Fluid (VOF) models through the volume finite method. The results show that the backflow phenomenon emerges from an inadequate SEN port design, when a boundary layer separation is generated before the steel is delivered to the mold. This separation occurs at the upper internal side of the port inducing a low pressure zone with high levels of kinetic energy dissipation, producing the backflow phenomenon. From the analysis, it is concluded that the implementation of a radius at the internal upper side of the port avoids the separation of the boundary layer, eliminating the backflow phenomenon which allows the use of the complete effective exit area of the port; this is reflected in a velocity decrease of the jets and consequently a velocity decrement of the bulk flow. Furthermore, the size of the radius controls the penetration angle of the jets, the impact point position and the meniscus deformation; which avoids the need of the inclination angle of the port.
Transient Mold Fluid Flow with Well- and Mountain-Bottom Nozzles in Continuous Casting of Steel
Metallurgical and Materials Transactions B, 2008
Nozzle shape plays a key role in determining the flow pattern in the mold of the continuouscasting process under both steady-state and transient conditions. This work applies computational models and experiments with a one-third scale water model to characterize flow in the nozzle and mold to evaluate well-bottom and mountain-bottom nozzle performance. Velocities predicted with the three-dimensional k-e turbulence model agree with both particle-image velocimetry and impeller measurements in the water model. The steady-state jet velocity and angle leaving the ports is similar for the two nozzle-bottom designs. However, the results show that nozzles with a mountain-shaped bottom are more susceptible to problems from asymmetric flow, low-frequency surface-flow variations, and excessive surface velocities. The same benefits of the well-bottom nozzle are predicted for flow in the steel caster.
Research on Intensity of Cooling Continuously Cast Steel by Water Nozzles
Acta Mechanica Slovaca, 2015
The article describes heat removal from the hot surface by water. Method of cooling in a secondary zone of continuous casting of steel has a significant influence on a quality of continuously cast products mainly from the point of view of internal and surface defects. For this reason, a physical model of the secondary zone has been developed at the Department of Thermal Engineering, which enables testing of both water and water-air nozzles. During laboratory modelling cooling effects of a nozzle have been expressed by means of two parameters. Most commonly used parameter is spray intensity, infrequently heat transfer coefficient is determined. In comparison with the cold model the energy and time consumption at measurements on the hot model are several fold higher. Therefore, also was found correlations between the two models.
NEW DESIGN OF SUBMERGED ENTRY NOZZLE FOR OPTIMIZING THIN SLAB CASTING PROCESS
New SEN design was developed for improving steel quality and/or increase caster productivity for thin slab caster in an operating industrial plant. The new design has two main advantages; first is to reduce turbulence under meniscus to ensure cleaner product that avoid flux/slag entrapment, while the second is the ability to increase the casting speed (productivity) with higher product quality. In this paper two finite element models are developed for quantitative and/or qualitative comparison between the new design and SEN design currently in use. The first model considers the SEN internal flow while the second is focused on the mold zone. The comparative study showed the gained superior performance when SEN middle web was removed, SEN port angled downward by 20° over the vertical one (0°). Furthermore, addition of small third downward port, to the main two sided ports enhanced the SEN performance through increasing the SEN depth, and mold width.