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A Numerical Investigation on VOD Nozzle Jets
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The metallurgic process, Vacuum Oxygen Decarburization (VOD) process, is used for producing stainless steels with ultra-low carbon grades. In a VOD process, an oxygen lance is equipped with a De Laval nozzle which injects high speed oxygen gas. The aim of this work is to increase the knowledge of the flow behavior in the harsh environment of VOD vessels. Two real VOD nozzles from industry were numerically studied and compared at different temperatures and ambient pressures.

 Flow patterns of the oxygen jet under different ambient pressures were studied and the flow information at different positions from the nozzle was analyzed. In addition, the study compared the effects of different ambient temperatures on the jet velocity and the dynamic pressure. The predictions revealed that the modeling results obtained with the CFD modeling showed an incorrect flow expansion, which agreed well with the results from the De Laval theory. Moreover, a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry have also been studied. It has been observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature has a positive effect on the improvement of the jet dynamic pressure.

For the comparison between the two nozzles concerned, the modeling results showed that one of the nozzles was more applicably proper for lower pressures, displaying a more stable flow pattern. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian curves.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , xii, 40 p.
Keyword [en]
VOD, nozzle, jet, vaccum, CFD
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-40596ISBN: 978-91-7501-066-3 (print)OAI: oai:DiVA.org:kth-40596DiVA: diva2:441611
Presentation
2011-09-14, Konferensrummet, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20110920Available from: 2011-09-20 Created: 2011-09-16 Last updated: 2011-09-20Bibliographically approved
List of papers
1. Mathematical Modeling of VOD Oxygen Nozzle Jets
Open this publication in new window or tab >>Mathematical Modeling of VOD Oxygen Nozzle Jets
2011 (English)In: Steel Research International, ISSN 1611-3683, Vol. 82, no 3, 249-259 p.Article in journal (Refereed) Published
Abstract [en]

This study has focused on numerically exploring the oxygen flow in the convergent-divergent De Laval nozzle. The De Laval nozzle has been commonly used as oxygen outlet at the lance tip in the vacuum oxygen decarburization (VOD) process. The nozzle geometry used in an active VOD plant was investigated by isentropic nozzle theory as well as by numerical modeling. Since an optimal nozzle design is only valid for a certain ambient pressure, one VOD nozzle will be less efficient for a large part of the pressure cycle. Different ambient pressures were used in the calculations that were based on the De Laval nozzle theory. Flow patterns of the oxygen jet under different ambient pressures were studied and the flow information at different positions from the nozzle was analyzed. In addition, the study compared the effects of different ambient temperatures on jet velocity and dynamic pressure. The predictions revealed that the modeling results obtained with the CFD modeling showed incorrect flow expansion, which agreed well with the results from the De Laval theory. Moreover, a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry have also been studied. It has been observed that an altering ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature has a positive effect on the improvement of the jet dynamic pressure.

Keyword
VOD, De Laval nozzle, Mathematical modeling, turbulence, jet domain, ambient pressure, flow pattern, jet width, ambient temperature
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-32592 (URN)10.1002/srin.201000108 (DOI)000289061100013 ()2-s2.0-79952234188 (Scopus ID)
Note
QC 20110420Available from: 2011-04-20 Created: 2011-04-18 Last updated: 2013-09-13Bibliographically approved
2. Mathematical comparison of two VOD nozzle jets
Open this publication in new window or tab >>Mathematical comparison of two VOD nozzle jets
2011 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 10, 1637-1646 p.Article in journal (Refereed) Published
Abstract [en]

Studies of physical phenomena in a jet caused by VOD (Vacuum Oxygen Decarburization) nozzles have been carried out. The VOD process is a metallurgical process where the steel-making route is controlled under vacuum environment with oxygen top blowing. In this work, two VOD nozzle models have been employed for an investigation based on two real De Laval geometries used in industry. Numerical modeling was used to study oxygen blowing states of the nozzles at different temperatures and ambient pressures. The nozzle models were numerically computed with two dimensional domains, where vacuum conditions and temperatures were specifically defined. The modeling results showed that one of the nozzles was more applicably proper for lower pressures, displaying a more stable flow pattern. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian curves.

Keyword
VOD, modeling, jet, blowing, pressure, temperature
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-40801 (URN)000296267500011 ()2-s2.0-82455184395 (Scopus ID)
Note
QC 20111115Available from: 2011-09-20 Created: 2011-09-20 Last updated: 2017-12-08Bibliographically approved

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