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Effects of gas jet instability on refractory wear: a study by high-speed photography
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
1992 (English)In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 21, no 1, p. 15-26Article in journal (Refereed) Published
Abstract [en]

To study influences of gas jet instability on tuyere refractory wear, gas injection was performed in an air-water system with a tuyere of 2 mm inner diameter. High-speed photography was used, with a framing rate of 8000 pictures per second, to film the tip region of a free and a half free tuyere. Characteristics of the cavity formed as a result of the jet instability were measured from the films, and the results were used in equations of bubble dynamics to calculate the pressure generated by the cavity motion. The film sequences show that as a result of the distortion of the gas-liquid interface, a throat in the gas jet is formed about 1.5D (tuyere i.d.) downstream of the tuyere tip. Radially moving gas starts to form an expanding cavity. The radius of the throat increases as it is pushed forward by the cavity expansion. With its radius reaching the maximum, the cavity stops growing. When the cavity collapses, bubble swarms are generated in the region near the tuyere. The cavity expands to 2D-4D (tuyere i.d.) within 1-15 ms. The maximum velocity of the expansion is about 10 m/s and acceleration ranges from 20 to 80 m/s2. The pressure calculated by using the cavity expansion data is in good agreement with the pressure measured at back-attack, which is around one half of the absolute pressure for the gas injection. This implies that the back-attack and cavity expansion are the same phenomenon. Passing the transition point of flow regimes the pressure increases very slowly as the injection rate increases. Occassionally, the cavity does not collapse immediately and it contracts after reaching the maximum radius. The cavity contraction generally takes longer than the expansion, with a velocity of about 2 m/s. The pressure reduction from the contraction is less than 0.1 bar which can not cause the formation of vapour bubbles in the liquid. By the cavity expansion, a liquid flow is set up which deforms and disintegrates gas bubbles nearby. At the moment of disintegration, liquid penetrates the concave side of the deformed bubble. The liquid flow may lead to an impact pressure of 30-90 bar in water and 210-630 bar in liquid steel. This pressure may cause refractory erosion with a pattern similar to that previously observed on H3BO3 disk surface. Besides the pitting erosion of the tuyere refractory, the influences of the jet instability on other factors of the refractory wear are also discussed.

Place, publisher, year, edition, pages
1992. Vol. 21, no 1, p. 15-26
National Category
Metallurgy and Metallic Materials Fluid Mechanics and Acoustics
Research subject
Process Metallurgy; Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-10647Local ID: 97af7e20-a330-11db-8975-000ea68e967bOAI: oai:DiVA.org:ltu-10647DiVA, id: diva2:983592
Note
Godkänd; 1992; 20070113 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

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Yang, QixingGustavsson, Håkan

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