Characteristics of Flow Field for Supersonic Oxygen Multijets with Various Laval Nozzle Structures
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THE oxygen lance is a main apparatus to deliver oxygen into a molten bath for the steelmaking process in a basic oxygen furnace (BOF) and an electric arc furnace (EAF). An impaction cavity is being formed by the supersonic oxygen jet at the surface of the molten bath. During this process, the kinetic energy of the molten bath is increased because of the oxygen jet, and the reaction of oxygen with carbon and phosphorus is also proceeding. Therefore, the oxygen lance plays an important role in facilitating the mixing effect of slag making, dephosphorization, and the decarburization process.[1–3] After the oxygen jet has passed through the Laval nozzle, its velocity increases up to approximately 2 Mach numbers and then decreases because of entrainment of an ambient gas. For a multihole oxygen lance, oxygen jets tend to swerve from a straight path and to merge with each other, representing a kind of multijet
FUHAI LIU is with the National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China and also with the Key Laboratory of Fluid Interaction with Material, Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected]. DONGBAI SUN and RONG ZHU are with the Key Laboratory of Fluid Interaction with Material, Ministry of Education, University of Science and Technology Beijing. YILIN LI is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Manuscript submitted February 21, 2019.
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evolution that restricts the oxygen jet impaction ability and, therefore, results in reduction of metallurgical and operational benefits.[4–7] Numerous studies of the behavior of oxygen jets under different conditions, including oxygen temperatures, Laval nozzle arrangements, and injection angles, have been carried out.[8–10] Wang et al.[11] showed, by means of experimental results and numerical simulations, that the oxygen preheating method could increase the impaction ability of a supersonic jet. Sambasivam et al.[12] reported a new structure of oxygen lance by inserting a subsonic nozzle to achieve a better process control and lower droplet generation rate. Higuchi and Tago[13] proposed that the lance nozzle with an appropriate twisted angle could generate a tangential force, improving the mixing effect in the molten bath. Sivells[14] reported, with a series of numerical simulations, that the Laval nozzle designed by means of a characteristic-line method could obtain a longer velocity potential core for the coherent jet with the same inlet pressure. In recent years,[15,16] the new Laval nozzle designed by means of the characteristic-line method was adopted in the EAF steelmaking process with good metallurgical benefits. The present study of the flow field characteristics of the oxygen jet using Laval nozzles of different structures is related to that of multihole oxygen lance dynamics. To obtain a better control
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