Water Model Experiments Research Articles

Continuous Casting Tundish Dead Volume Study by Physical Modeling and Computational Investigation

Flow efficiency in a two‐strand continuous casting tundish is studied by analyzing the residential time distribution (RTD) curves in a small‐scale tundish water model using a conductive NaCl solution tracer. The velocity fields in the tundish water model are measured by particle image velocimetry, which is used to validate the results of the mathematical model in the article. It is found that the tracer concentration has a significant impact on the predicted dead volume fraction in the RTD analysis. Validated mathematical modeling of the computational fluid dynamics (CFD) technology is performed to explore the root cause of the defective results in the RTD analysis. It is found that the flow inside the tundish is sensitive to density variations caused by the injected tracer. A denser tracer will stay lower in the tundish by gravity and flow out of the tundish more quickly. A proper tracer concentration in the water model experiments is discussed to visualize the dead volume and improve tundish furniture design efficiently for future work, a new method using CFD modeling is proposed in this article, which can directly demonstrate the dead volume's location.

Thermodynamic and Kinetic Behavior Study of Gas Bubbles in High‐Temperature Steel Melts

This study provides an exhaustive exploration of the thermal expansion of low‐temperature argon bubbles in high‐temperature molten steel and the resulting dynamic effects. The energy equation of compressible fluid simultaneously with the volume of fluid model under the Euler framework is solved. The generation and rising behavior of bubbles are validated through rigorous physical water model experiments. Findings reveal that, within a heating time of 0.2–0.45 ms, gas bubbles already complete 65–90% of their internal energy increase. The total heat transfer time and heat transfer coefficient of bubbles exhibit distinctive patterns influenced by the initial diameter and temperature of the bubbles. Specifically, under the conditions studied, bubbles exhibit a total heat transfer time of ≈20–60 ms, accompanied by a heat transfer coefficient ranging from 500 to 2600 W (m2 * K)−1. During the thermal expansion process, gas bubbles experience energy transfer and conversion within the two‐phase flow. This article establishes a dynamic model describing bubble thermal expansion in steel melts based on underwater bubble dynamics’ first principles. The model provides a quantitative depiction of instantaneous changes in bubble size, velocity, and kinetic energy under specific conditions.

Multi-field coupling vibration patterns of the multiphase sink vortex and distortion recognition method

Fluid-induced vibration sensing technology plays an essential role in the safety and stable operation of fluid control equipment. The sensing works oriented to the multiphase sink vortex-induced vibration (MSVIV) face significant challenges in state recognition, such as the aero-engine oil pipe, metallurgical casting ladle, and microfluidic equipment. This paper presents a multi-field coupling vibration modelling and solving strategy to investigate the MSVIV transition patterns. Based on the volume of fluid and level set method, an efficient volume-correction strategy is presented to consider the mass variation and keep velocity fields without divergence. Then, a fluid–structure-acoustic dynamic model is conducted to explore multiphase vortex transport regularities. Considering the solution singularity of the fluid–solid-acoustic coupling system, a residue theorem-based solution strategy is presented to obtain the MSVIV evolution behaviors. Finally, a multichannel sensing MSVIV water-model experiment (MSVIV-WME) platform is conducted to verify the above results, and a wavelet transform-based processing approach can be utilized to obtain mutation energy features. Research results illustrate that the proposed strategy has revealed the MSVIV transition behaviors. The MSVIV process in critical states dominates nonlinear vibration patterns. The self-development sensing platform can monitor the MSVIV evolution process in real-time, and the wavelet transform-based sensing attribute with the dw3 frequency band can identify distortion characteristics. Relevant results can offer useful references for MSVIV state recognition and offer technical solving strategies for microfluidics monitoring equipment.

Impact of bottom-blowing parameters on melt pool homogenization in a 120-ton converter based on carbon-oxygen reaction

This paper studies a 120 t converter, focusing on the influence of the CO bubbles generated by the carbon-oxygen reaction during the decarburization process on the stirring action of the melt pool. It examines the effect of the intensity and arrangement of bottom blowing on the homogenization effect, taking into account the dynamics of CO bubbles generated from the carbon-oxygen reaction. Initially, a macroscopic kinetics model for the generation of CO bubbles during the carbon-oxygen reaction in converter steelmaking is established. Subsequently, a water model simulation device for CO bubble generation from the converter's carbon–oxygen reaction is designed, establishing a 120 t converter water model experimental setup with a similarity ratio of 1:8. The main indicator for evaluating the homogenizing effect of the converter is the mixing time, based on which, experimental schemes are designed. Water model experiments are conducted to study the influence of bottom-blowing flow and nozzle arrangement on the melt pool's stirring flow field under the action of carbon-oxygen reaction. The results show that greater generation intensity of CO bubbles from the carbon-oxygen reaction leads to shorter mixing time in the melt pool; when the angular spread of the bottom-blowing elements is small, the bottom-blowing gas flow is relatively concentrated, facilitating stirring in the melt pool. However, increasing the angular spread of the nozzles to a certain extent leads to the dispersion of bottom-blowing energy, making it difficult to form effective stirring; when the bottom-blowing flow is less than 1.5 Nm3/h, the mixing time of the melt pool decreases with the increase of bottom-blowing flow; when the bottom-blowing flow is greater than 1.5 Nm3/h, the mixing time of the melt pool increases with the increase of bottom-blowing flow. In addition, a series of industrial experiments were carried out, and the research results were applied to the actual production process. By comparing the test results after the optimization scheme with the production data of the original process, it was found that the optimization scheme significantly improved the smelting efficiency and reduced the production cost. These research results not only provide a theoretical basis, but also provide practical guidance for the optimization of converter smelting process.

Physical Model of Inclusions Removal at Static Steel-Slag Interface.

Inclusions are one of the important factors affecting the cleanliness of molten steel. The current optimization of inclusion removal methods mainly focuses on promoting inclusions to float to the slag-steel interface so that the inclusions can be absorbed and removed by the refining slag. However, the research on the floating removal of inclusions cannot be carried out directly in the ladle, so methods such as mathematical models and physical models were developed. This article uses silicone oil to simulate the slag layer; polypropylene particles; and aluminum oxide particles to simulate inclusions to establish a water model experiment. By changing the viscosity of silicone oil and the diameter of particles, the factors affecting the movement of inclusions at the slag-steel interface were explored. Based on the water model, a mathematical model of the floating behavior of inclusions at the slag-steel interface was constructed, and parameters such as particle diameter and interfacial tension in the water model experiment were studied by the mathematical model for calculation. Both the mathematical model and the water model experimental results show that after the viscosity of silicone oil increases from 0.048 Pa·s to 0.096 Pa·s, the dimensionless displacement and terminal velocity of the particles decreases. When the diameter of the same particle increases, the dimensionless displacement and terminal velocity increases. The dimensionless displacement of polypropylene particles of the same diameter is larger than that of aluminum oxide particles, and the terminal velocity is smaller than that of aluminum oxide particles. This is attributed to the better overall three-phase wettability of polypropylene particle. When the liquid level increases, the dimensionless displacement and terminal velocity of particles under the same conditions show only slight differences (less than 10%).

Continuous casting tundish quality study by mathematical & physical simulations, economics with plant result justifications

A combination of physical modeling, computational fluid dynamics modeling, and economics with plant trial studies was performed for quality improvement of Special Bar Quality (SBQ) and Oil Country Tubular Goods (OCTG) grade tundish steels. The present study consists of operating parameters like inert gas shrouding, non-isothermal conditions, and flow control devices (FCD) used on the billet product and slab quality. This work uses mathematical modeling using the fluid volume and discrete phase method (DPM) and the standard k-ε turbulence model validated with one-third scale physical water model experiments. A strong correlation between the physical model and computational simulation was found with rejection ratio and inclusion counts. Data about customer demands correlated with operating parameters for proper plant insights with an economic study to predict the cost-related issue. With the incorporation of FCD, the weight of the tundish skull was reduced by 6–10 M USD/year with a simulation studies expenditure of around 200 K. FCD also reduced the customer complaint index (CCI).

Effect of Differential Flow Blowing Argon and Nozzle Position on Mixing Time and Slag Eye in Dual Nozzle Ladle Using Water Model Experiment

Effect of Differential Flow Blowing Argon and Nozzle Position on Mixing Time and Slag Eye in Dual Nozzle Ladle Using Water Model Experiment

CFD simulation and water model experiments with overflow-type supergravity reactor set up for continuously removing inclusions from aluminum melt

In this work, an overflow-type supergravity reactor has been tested for removal of inclusions from aluminum melt. A combination of numerical and physical simulations was employed to investigate the continuous separation process of recycled aluminum melt and inclusions, with a focus on evaluating the effects of reactor structures, process parameters, and inclusion characteristics on the inclusion separation efficiency. The results of numerical simulation indicate that the inclusion separation efficiency is positively related to overflow pipe length (L), overflow pipe installation height (H), gravity coefficient (G), inclusion density (ρ) and inclusion diameter (d), and negatively related to overflow pipe diameter (Φ) and melt inflow rate (Q). The overflow-type supergravity reactor exhibited excellent performance in separating inclusions from recycled aluminum melt. Under the conditions of L = 40 mm, H = 108 mm, Φ = 10 mm, G = 500, and Q = 0.5 kg/s, the separation efficiency of 18 μm Al2O3 inclusions reached nearly 100 %. The high consistency between the results of numerical and physical simulations provided full verification of the reliability and accuracy of the numerical simulation.

Assessment of URANS-Type Turbulent Flow Modeling of a Single Port Submerged Entry Nozzle (SEN) for Thin Slab Continuous Casting (TSC) Process

The numerical methods based on the unsteady Reynolds-averaged Navier–Stokes (URANS) equations are robust tools to model the turbulent flow for the industrial processes. They allow an acceptable grid resolution along with reasonable calculation time. Herein, the URANS approach is validated against a water model experiment for the special single port submerged entry nozzle (SEN) design used in the thin slab casting (TSC) process. A 1-to-2 under-scaled water model was constructed, including the SEN, mold, and strand Plexiglas segments. Paddle-type sensors were instrumented to measure the submeniscus velocity supported by videorecording of the dye injections to provide both qualitative and quantitative verification of the SEN flow simulations. Two advanced URANS-type models (realizable k–ε and shear stress transport k–ω) were applied to calculate velocity pattern on meshes with various resolutions. An oscillating single jet flow was detected in the experiment, which the URANS simulations initially struggled to reflect. The dimensionless analysis of the mesh properties and corresponding adjustment of the boundary layers inside the SEN allowed to resolve the flow pattern. The performed fast Fourier transform (FFT) verified a good numerical prediction of the flow frequency spectrum. The corresponding simulation strategy is proposed for the industrial CC process using the URANS approach.

Stabilizing Flow of Molten Steel in Mold during Slab Continuous Casting through Electromagnetic Swirling Flow in Nozzle

Bias flow of molten metal in slab mold caused by unstable flow from submerged entry nozzle can deteriorate the slab quality during continuous casting. In this study, a novel electromagnetic swirling flow in nozzle (EMSFN) technique, which utilizes electromagnetic force to stabilize the flow in the nozzle and subsequently control the flow in the mold, is proposed. The mechanism for controlling unstable flow through EMSFN is explored through numerical simulation and water model experiments. In the results, it is shown that the molten steel is rotated under the effect of magnetic field and flows into the mold along the upper edge of the nozzle outlet, which weakens the impact of molten steel on the bottom of nozzle and stabilizes the outflow from nozzle. The flow field is consistently symmetrical on both sides of the nozzle. The impact depth of molten steel flowing down along the narrow sides of the mold on both sides is greatly reduced. The surface velocity on both sides of the nozzle changes uniformly. The range of surface velocity variation with EMSFN is only 10% of that with a conventional nozzle. The EMSFN technique can help prevent slag entrapment and improve the flotation of inclusions and bubbles.

Understanding of baffle effect of inserting a filter within a tundish via a water model experiment and numerical simulation

The baffle effect of inserting a filter within a tundish was investigated using a combination of water model experiments and numerical simulations. The filter, which is a cost-effective device used to enhance the quality of molten steel by removing inclusions, was studied for its impact on the removal rate of inclusions. In the water model experiments, a scaled-down model of the tundish system was created with a geometric ratio of 1:4. Polyethylene particles of varying sizes were used to simulate the inclusions. Additionally, a three-dimensional numerical model of the water model was developed to validate the experimental findings, provide supplementary data for analysis, and propose an optimized tundish configuration by moving the weir away from the filter by 50, 100, and 150 mm. The flow patterns were also thoroughly examined. The results revealed that the presence of the filter increased the flow resistance within the tundish, leading to changes in the residence time distribution. This resulted in the formation of a ‘dead zone’ with a significantly prolonged residence time. The higher flow resistance hindered the entry and exit of particles from the last chamber of the tundish. As a result, the distribution of particles in the last chamber became more dispersed, reducing the detrimental effects of inclusions in the steel. The removal efficiency of the seven types of particles was improved by 2–7%. Furthermore, by moving the weir away from the filter by 50 mm, the removal ratio could be further increased by approximately 2%.

Optimization of mixing behaviors in a multistage vanadium shale leaching tank by a double-layer impeller at different speeds

BackgroundMultistage vanadium-containing shale leaching tanks often suffer from uneven solid phase distribution and mineral deposition at the bottom of the tank, leading to low leaching efficiency. MethodsIn this study, the solid‒liquid flow, tracer diffusion and power consumption in a multistage vanadium shale leaching tank with an inlet and outlet were numerically investigated and compared, the samples were stirred by a double-layer impeller with the same and different speeds, and the numerical model was validated by water model experiments. Significant FindingsThe results showed that the maximum velocity near the liquid surface increased from 1.24 m/s to 1.47 m/s and the average velocity increased from 1.15 m/s to 1.24 m/s when the lower impeller speed increased from 34 r/min to 44 r/min. The volume of the low-speed region decreased from 1.15 m3 to 0.63 m3, and the stirring power was reduced by 14.7%. In addition, increasing the lower impeller speed could effectively shorten the response time and increase the peak molar concentration of the tracer. A stirring speed of 34 rpm for the upper impeller and 44 rpm for the lower impeller could achieve good stirring efficiency with proper stirring power.

Numerical Simulation of Flow and Argon Bubble Distribution in a Continuous Casting Slab Mold under Different Argon Injection Modes

A three-dimensional model is established to investigate the effect of argon injection mode, argon flow rate and casting speed on the gas–liquid two-phase flow behavior inside a slab continuous casting mold. The Eulerian–Eulerian model is employed to simulate the gas–liquid flow, and the population balance model is applied to describe the bubble breakage and coalescence process in the mold. The numerical simulation results of the bubble size distribution are verified using the water model experiment. The results show that the flow field and bubble distribution are similar between the argon injection at the upper submerged entry nozzle (SEN) and tundish upper nozzle (TUN), while the number density is larger for the argon injection of TUN. The coalescence rate of bubbles and the bubble size inside the mold increase with increasing argon flow rate. When the argon flow rate exceeds 4 L/min, the flow pattern of liquid steel changes from double-roll flow to complex flow, with aggravation of the level fluctuation of the top surface near the SEN. When the casting speed increases, the bubble breakup rate increases and results in a decrease in the size of bubbles inside the mold. At a high casting speed, the flow pattern tends to form double-roll flow, and the liquid level at the narrow face of the top surface increases.

Process optimization of bottom-blown argon for 130t ladle furnace

ABSTRACT A quarter scale water model experiment is employed to investigate the effect of single and double porous plug placement and blowing flow rates on the mixing time, slag eye area, and slag entrapment depth. As a result, when the blowing flow rate is greater than 180 L min–1, the blowing effect of double blowing plugs is better than that of single blowing plugs. The open eye area and slag entrapment depth in the double blow plug arrangement are smaller than that in the single blow plug arrangement. In general, the ladle refining effect is better when the blow plug is arranged at 0.4R position and the angle between the two blow plugs is 120°. The final recommended argon blowing process is 240–300 L min–1 for the heating and alloying process and 60–120 L min–1 for the soft blowing process, respectively.

Influence of mould level instability on the unevenness of solidified shell deformations during continuous casting

ABSTRACT The influence of mould level instability during continuous casting on the unevenness of the initial solidified shell in hypo-peritectic steels has been investigated. Water model experiments and in-plant casting experiments revealed that mould level instability, which increases with increasing casting speed, is related to longitudinal cracking resulting from the unevenness of the solidification shell. A numerical model which considers the effect of mould level instability was developed and used to simulate the formation of the unevenness of the solidification shell and solidified shell deflections. The calculation results show that an increase in the non-uniform infiltration of mould flux increases the unevenness of the solidified shell. On the other hand, the unevenness of the solidified shell decreases due to mild cooling. Overall, the results of the plant tests and calculations show that non-uniform infiltration of mould flux dramatically affects air gap formation and the unevenness of the solidified shell.

Experimental and numerical investigations of particle suspension suppression mechanisms for a particle-suppression device in a stirred liquid bath

Particle suspension in a turbulent flow can seriously affect the performance of manufactured products in many industrial processes in which the motion of particles cannot be modeled using the numerical method because of the enormous number of particles. Therefore, in this study, a full-scale computational fluid dynamics (CFD) simulation and a 1/5 scaled-down water model experiment were employed to investigate the flow pattern and dynamic behavior of particles in a continuously stirred vessel system. Based on the understanding of the suspension mechanism of settling particles, a particle-suppression device was designed to realize the harmless movement and deposition of particles. The results showed that the flow guidance and division mechanisms of the particle-suppression device led to the inhibition of particle suspensions. In addition, the optimal parameter combination for the device from the water model experiment combined with the orthogonal experimental design, resulted in a 98.3% reduction in the concentration of suspended particles. The suspension of particles was effectively suppressed, which improves product quality and production efficiency. Reliable results can be achieved by combining CFD simulations and water model experiments.

Demonstration Experiments on Grain Refinement Caused by Vibration Mold Using Ammonium Chloride Solution

For the purpose of understanding the mechanism of grain refinement in cast metal by mechanical vibration, demonstration tests were conducted using an ammonium chloride solution. Ammonium chloride solution and molds with various shape were prepared for the water model experiment. In the case of an open mold, ammonium chloride crystals crystallized on the mold wall and grew toward the center of the mold without vibration. However, when vibration was applied, countless crystals generated at the upper side of the solution immediately after pouring. In the case of a full plugged mold, no wave and convection occurred in the solution even when vibration was added, and the behavior seen was similar to the case without vibration. When only convection occurred in the full plugged mold, crystals were found to move from the mold wall into the solution. When a weir was set in the riser, it helped prevent the generation of crystals on the mold wall of the riser from migrating to the specimen. When a mold with a weir was used for Al–2%Cu alloy, crystals in the specimen did not become refined as seen in the water model experiments.

A New Insight into the Flow and Pressure Behavior of a Stopper Rod Flow Control System

A previously unnoticed anomaly is recently identified in a stopper rod flow control system for the continuous casting of steel by comparing full‐scale water model experiments with plant data. Despite extensive research previously done on the continuous casting fluid flow phenomena, this anomaly and its background physics are not well understood by researchers. Computational fluid dynamics (CFD) modeling of the molten steel flow in the stopper rod system is performed with predictions matching closely with water model data but deviating from plant measurements. It is thus suggested by this comparison that certain aspects of the liquid steel flow and pressure behavior in the stopper rod system cannot be effectively described by traditional modeling techniques due to their embedded limitations. Through water modeling, CFD simulations, plant measurements, and theoretical analysis, the current study for the first time presents a thorough discussion of this observed anomaly, which brings new insights into understanding the complex fluid flow behavior and pressure distributions inside the stopper rod control system during the continuous casting process.

Numerical Analysis for Interaction of Fluid and Sphere Penetrating into Liquid Bath

In the steelmaking process, it is necessary to decrease impurities in steel to meet the increasing demand for high-grade products. Top blowing and blasting of powder reagent are desirable for the purpose and the deeper penetration of particles into the bath is important for efficient refining. In the present work, CFD calculation with VOF (Volume of Fluid) method and dynamic mesh was executed to study the reported penetration and residual bubble behavior of polypropylene sphere (diameter of 9.6 mm) with a static contact angle of 87° and 143° and an entry solid sphere velocity of 0.63, 0.89, and 1.53 m/s in the water model experiments. Calculated results showed the numerical analysis could evaluate the formation and breakup of air column behind the sphere and the generation of consequent residual bubble on the sphere. Good wettability and high entry speed promoted the deeper penetration of the sphere. Calculated dynamic contact angle on the basis of Kistler’s model indicated that the difference between static and dynamic contact angles was within 13.7° in the present conditions and the discrepancy could not wield a substantial influence on the result of CFD calculation. The adoption of base and refined mesh without parallel zone around the sphere could not give a good agreement with the experimental results. On the other hand, the use of layer mesh was appropriate for reproducing the penetration depth and residual bubble volume observed in the experiments.

Enhanced Productivity of Bottom-Blowing Copper-Smelting Process Using Plume Eye

Bottom-blowing copper smelting is a bath smelting technology recently developed in China. It has the advantages of good adaptability of raw materials, high oxygen utilization and thermal efficiency, and flexible production capacity. Plume eye is a unique phenomenon observed in the bottom-blowing copper-smelting furnace where the slag on the surface of the bath is pushed away by the high-pressure gas injected from the bottom. The existence of plume eye was first confirmed by analyzing the quenched industrial samples collected above the gas injection area and then investigated by laboratory water model experiments. Combining the plant operating data and the smelting mechanism of the copper concentrate, the role of the plume eye in bottom-blowing-enhanced smelting is analyzed. It reveals that the direct dissolution of copper concentrate as a low-grade matte into the molten matte can significantly accelerate the reactions between the concentrate and oxygen. The productivity of the bottom-blowing furnace is therefore increased as a result. The effects of the gas flow rate and thickness of the matte and of the slag layer on the diameter of the plume eye were studied using water-model experiments. It was found that increasing the gas flow and the thickness of the matte and reducing the thickness of the slag can increase the diameter of the plume eye. This work is of great significance for further understanding the copper bottom-blowing smelting technology and optimizing industrial operations.