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A Study of the Swirling Flow Pattern when Using TurboSwirl in the Casting Process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.ORCID iD: 0000-0002-4081-7766
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of a swirling flow can provide a more uniform velocity distribution and a calmer filling condition according to previous studies of both ingot and continuous casting processes of steel. However, the existing swirling flow generation methods developed in last decades all have some limitations. Recently, a new swirling flow generator, the TurboSwirl device, was proposed. In this work, the convergent nozzle was studied with different angles. The maximum wall shear stress can be reduced by changing the convergent angle between 40º and 60º to obtain a higher swirl intensity. Also, a lower maximum axial velocity can be obtained with a smaller convergent angle. Furthermore, the maximum axial velocity and wall shear stress can also be affected by moving the location of the vertical runner. A water model experiment was carried out to verify the simulation results of the effect of the convergent angle on the swirling flow pattern. The shape of the air-core vortex in the water model experiment could only be accurately simulated by using the Reynolds Stress Model (RSM). The simulation results were also validated by the measured radial velocity in the vertical runner by the ultrasonic velocity profiler (UVP). The TurboSwirl was reversed and connected to a traditional SEN to generate the swirling flow. The periodic characteristic of the swirling flow and asymmetry flow pattern were observed in both the simulated and measured results. The detached eddy simulation (DES) turbulence model was used to catch the time-dependent flow pattern and the predicted results agree well with measured axial and tangential velocities. This new design of the SEN with the reverse TurboSwirl could provide an almost equivalent strength of the swirling flow generated by an electromagnetic swirling flow generator. It can also reduce the downward axial velocities in the center of the SEN outlet and obtain a calmer meniscus and internal flow in the mold.

Abstract [sv]

Tidigare studier visar att ett roterande flöde kan ge en mer likformig hastighetsfördelning och en lugnare fyllning i både göt- och stränggjutning av stål. De befintliga metoderna för att generera ett roterande flöde har vissa begränsningar. En ny metod för att generera det roterande flödet, en så kallad TurboSwirl, föreslogs nyligen. I detta arbete undersöktes ett konvergent munstycke med olika vinklar för att se hur detta påverkade det roterande flödet som genererades i anordningen. Resultaten visar att skjuvspänningen i systemet kan reduceras genom att ändra munstyckets vinkel mellan 40º till 60º. En lägre maximal axiell hastighet kan också uppnås med en mindre konvergent vinkel på munstycket. Det är även möjligt att påverka den maximala axiella hastigheten och skjuvspänningen i systemet genom att förflytta den vertikala kanalen i anordningen. Vattenmodellexperiment har utförts för att validera simuleringsresultaten. Det kraftigt roterande flödet kunde endast beskrivas väl av Reynolds Stress Model (RSM). Validering utfördes också genom att mäta den radiella hastigheten i den vertikala kanalen med en Ultrasonic Velocity Profiler (UVP). TurboSwirl-anordningen vändes och kopplades till gjutröret för att generera det roterande flödet. Detta studerades både med numeriska modeller och med vattenmodellering. Ett periodiskt asymmetriskt roterande flöde observerades både i numeriska modellerna och i vattenmodellerna. För att modellera detta periodiska flöde så användes detached eddy simulation (DES) modellen. Resultaten då denna modell användes stämmer väl med de experimentella mätningarna. Denna nya design med TurboSwirl kan uppnå liknande styrka på det roterande flödet som när elektromagnetisk omrörning användes. Det resulterande roterande flödet leder till en lägre axiell hastighet i gjutröret samt en lugnare yta och ett lugnare flöde i kokillen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 70 p.
Keyword [en]
flow pattern, swirling flow, TurboSwirl, CFD, turbulence models, water model
Keyword [sv]
flödesmönster, roterandeflöde, TurboSwirl, CFD, turbulensmodeller, vattenmodell
National Category
Metallurgy and Metallic Materials
Research subject
Metallurgical process science
Identifiers
URN: urn:nbn:se:kth:diva-196806ISBN: 978-91-7729-211-1OAI: oai:DiVA.org:kth-196806DiVA: diva2:1048871
Public defence
2016-12-16, M311, Brinellvägen 68, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161123

Available from: 2016-11-23 Created: 2016-11-22 Last updated: 2016-11-23Bibliographically approved
List of papers
1. Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process
Open this publication in new window or tab >>Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process
2015 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 6, 2652-2665 p.Article in journal (Refereed) Published
Abstract [en]

To produce high-quality ingot cast steel with a better surface quality, it would be beneficial for the uphill teeming process if a much more stable flow pattern could be achieved in the runners. Several techniques have been utilized in the industry to try to obtain a stable flow of liquid steel, such as a swirling flow. Some research has indicated that a swirl blade inserted in the horizontal and vertical runners, or some other additional devices and physics could generate a swirling flow in order to give a lower hump height, avoid mold flux entrapment, and improve the quality of the ingot products, and a new swirling flow generation component, TurboSwirl, was introduced to improve the flow pattern. It has recently been demonstrated that the TurboSwirl method can effectively reduce the risk of mold flux entrapment, lower the maximum wall shear stress, and decrease velocity fluctuations. The TurboSwirl is built at the elbow of the runners as a connection between the horizontal and vertical runners. It is located near the mold and it generates a tangential flow that can be used with a divergent nozzle in order to decrease the axial velocity of the vertical flow into the mold. This stabilizes flow before the fluid enters the mold. However, high wall shear stresses develop at the walls due to the fierce rotation in the TurboSwirl. In order to achieve a calmer flow and to protect the refractory wall, some structural improvements have been made. It was found that by changing the flaring angle of the divergent nozzle, it was possible to lower the axial velocity and wall shear stress. Moreover, when the vertical runner and the divergent nozzle were not placed at the center of the TurboSwirl, quite different flow patterns could be obtained to meet to different requirements. In addition, the swirl numbers of all the cases mentioned above were calculated to ensure that the swirling flow was strong enough to generate a swirling flow of the liquid steel in the TurboSwirl.

Place, publisher, year, edition, pages
Springer, 2015
Keyword
SWIRLING FLOW, IMMERSION NOZZLE, FLUID-FLOW, MOLD, PATTERN, BLADE, GENERATOR, TUNDISH. DESIGN
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-180621 (URN)10.1007/s11663-015-0445-4 (DOI)000367067600027 ()2-s2.0-84946489524 (ScopusID)
Note

QC 20160120

Available from: 2016-01-20 Created: 2016-01-19 Last updated: 2016-11-22Bibliographically approved
2. An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process
Open this publication in new window or tab >>An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process
2016 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 8, 1404-1412 p.Article in journal (Refereed) Published
Abstract [en]

A swirling flow has been demonstrated to be beneficial for making the flow pattern even and to reduce turbulence during filling in ingot casting. A new swirling flow generation device, TurboSwirl, was applied to improve the flow pattern of the liquid steel as it flows into the mold so that a more stable flow could be obtained. A water model was built including the TurboSwirl with different flaring angles of the divergent nozzle, according to a former numerical study indicating that a much more beneficial flow pattern could be obtained by reducing the flaring angle. To validate the mathematical model, the air-core vortex formed in the water model experiment was used, and the length of the vortex was measured and compared to the numerical predictions. Different turbulence models including the standard k-epsilon, realizable k-epsilon and Reynolds stress model were tested. It was found that only the Reynolds stress model could most accurately simulate the high swirling flow including a vortex. In addition, the radial velocity of the water around the vortex was measured by an ultrasonic velocity profiler (UVP). The experimental results revealed a high turbulence of the swirling flow and strong fluctuations of the vortex. The radial velocity of the water around the upper part of the vortex could be predicted well compared to the experimental results by the UVP measurements.

Place, publisher, year, edition, pages
Iron and Steel Institute of Japan, 2016
Keyword
water model, ingot casting, TurboSwirl, swirling flow, vortex, ultrasonic velocity profiler
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-192774 (URN)10.2355/isijinternational.ISIJINT-2016-093 (DOI)000381847200012 ()2-s2.0-84984918512 (ScopusID)
Note

QC 20160926

Available from: 2016-09-26 Created: 2016-09-20 Last updated: 2016-11-22Bibliographically approved
3. Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process
Open this publication in new window or tab >>Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process
2016 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed) Accepted
Abstract [en]

As an alternative to some traditional methods to generate a swirling flow in the continuous casting process, the use of a new swirling flow generator, TurboSwirl, was studied. Specifically, a reversed TurboSwirl device was designed as part of a submerged entry nozzle (SEN) for a round billet continuous casting process. Mathematical modelling was used to investigate this new design and a water model experiment was carried out to validate the mathematical model. The predicted velocities by the turbulence models: realizable k-ε model, Reynold stress model (RSM) and detached eddy simulation (DES) were compared to the measured results from an ultrasound velocity profile (UVP) method. The DES model could give the best prediction inside the SEN and had a deviation less than 3.1% compared to the measured results. Moreover, based on the validated mathematical model and the new design of the SEN, the effect of the swirling flow generated by the reverse TurboSwirl on the flow field of the SEN and mold was compared to the design of the electromagnetic swirl flow generator (EMSFG). A very strong swirling flow in the SEN and a stable flow pattern in the mold could be obtained by the reverse TurboSwirl compared to the EMSFG. 

Keyword
swirling flow, TurboSwirl, SEN, water model, UVP
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-196832 (URN)10.1002/srin.201600339 (DOI)
Note

QC 20161123

Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2016-11-23Bibliographically approved
4. Numerical Study of the Application for the Divergent Reverse TurboSwirl Nozzle in the Billet Continuous Casting Process
Open this publication in new window or tab >>Numerical Study of the Application for the Divergent Reverse TurboSwirl Nozzle in the Billet Continuous Casting Process
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The swirling flow is demanded from the submerged entry nozzle (SEN) to the mold for the continuous casting process. A new design of the SEN is applied by using the reverse TurboSwirl. The TurboSwirl has been proved that it can provide a more stable flow pattern of the liquid steel in the mold. It also can supply a strong enough swirling flow compared to other swirling flow generation methods. Furthermore, a divergent nozzle is added to replace the bottom part of the straight SEN. This new divergent reverse TurboSwirl nozzle (DRTSN) could gain a more beneficial flow pattern in the mold compared to the straight nozzle. The numerical results reveals that a stronger swirling flow can be gained at the SEN outlet with a calmer flow field and active meniscus flow. It is also found that the swirl intensity in the SEN is independent of the casting speed. Lower casting speed is more desired due to a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. Longer horizontal runner can supply a more uniform velocity profile and symmetrical flow pattern in the mold. 

Keyword
swirling flow, TurboSwirl, divergent nozzle, SEN, billet continuous casting
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-196833 (URN)
Note

QC 20161123

Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2016-11-23Bibliographically approved

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