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A study of flow fields during filling of a sampler
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized.

The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , 34 p.
Series
KTH/MSE--09/19--SE+APRMETU/AVH
Keyword [en]
physical modeling, flow pattern, vortex, filling, PIV, sampler, simulation, turbulence, Wilcox k-ω model
National Category
Materials Engineering Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-10693ISBN: 978-91-7415-330-9 (print)OAI: oai:DiVA.org:kth-10693DiVA: diva2:225379
Presentation
2009-06-02, B23, KTH, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-06-30 Created: 2009-06-26 Last updated: 2010-11-03Bibliographically approved
List of papers
1. Physical modeling of a sampler filling for molten steel
Open this publication in new window or tab >>Physical modeling of a sampler filling for molten steel
2009 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 10, 1522-1529 p.Article in journal (Refereed) Published
Abstract [en]

In recent years, much attention has been paid to determining not only the composition, but also the inclusion characteristics from liquid steel samples extracted from a ladle or a tundish. Here, a crucial point is that the steel sampler is filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process. In this paper, this is done using physical modeling of a lollipop-shaped sampler. More specifically, particle image velocimetry was employed to capture the flow field and calculate the velocity vectors during the entire experiment. The filling rate at the pin part of the sampler was varied during the experiments. It was found that due to the geometry change at the transition from the inlet pin to the body part of the sampler, the flow is very chaotic at the initial filling stage. Furthermore, vortexes are formed in the water sampler vessel during all the fillings and the height of the vortex center varies with the filling rate. Overall, it was found that the flow patterns in the lollipop-shaped sampler vessel can be characterized into three distinct flow regions: the upper vortexes region, the lower horizontal flow region and the middle nozzle flow region.

Keyword
Flow pattern, Physical modeling, PIV, Sampler, Vortex
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24398 (URN)10.2355/isijinternational.49.1522 (DOI)000271176100009 ()2-s2.0-73949145212 (Scopus ID)
Note
QC 20100907. Tidigare titel “Physical Modeling of a Sampler Filling”.Available from: 2010-09-07 Created: 2010-09-07 Last updated: 2017-12-12Bibliographically approved
2. Mathematical Modelling of Water Sampler Filling
Open this publication in new window or tab >>Mathematical Modelling of Water Sampler Filling
2010 (English)In: Steel Research International, ISSN 1611-3683, Vol. 81, no 2, 112-122 p.Article in journal (Refereed) Published
Abstract [en]

Steel samples taken from ladles or tundishes during the steel making process can be of significant importance when monitoring the inclusion size and distribution. In order to preserve the original size and distributions of inclusions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Thus, it is necessary to investigate the flow during a sampling process to make sure that this is minimized. In addition, it is important to study the turbulence characteristics, since it is known to influence the inclusion growth. This study presents mathematical modelling of sampler filling using water as a media and experimental results for verification. The study focuses on a lollipop-shaped sampler since it is one of the most common in the industry. The sampler is filled from an inlet pin located at the bottom centre of the main body. In addition, two different turbulence models, the realizable k-ε model and Wilcox k-ω model, were used to study the flow pattern in the sampler. The predictions were compared to experimental results obtained by Particle Image Velocimetry (PIV) measurements. It was found that the flow field predictions using the Wilcox k-ω model agreed best with the flow field obtained by PIV measurements. Furthermore, it was illustrated that the Wilcox k-ω model can be used for predictions of the different flow regions as well as the positions of the centres of vortexes which are located near the free surface. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.

Keyword
sampler, filling, simulation, flow pattern, turbulence, vortex, Wilcox k-ω model
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24413 (URN)10.1002/srin.200900085 (DOI)000275142400004 ()2-s2.0-77949430978 (Scopus ID)
Note
QC 20100907Available from: 2010-09-07 Created: 2010-09-07 Last updated: 2011-11-06Bibliographically approved

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