Effect of Ambient and Oxygen Temperature on Flow Field Characteristics of Coherent Jet
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OXYGEN supplied to the molten bath through oxygen lance is a main characteristic in steelmaking processes such as the basic oxygen furnace (BOF) and the electric arc furnace (EAF). The oxygen jets play an important role in decarburization, rapid heating, foaming slag formation, and stirring liquid melt inside the furnace. In order to get better stirring effect and bigger impacting cavity, Laval nozzles are preferred to increase the momentum of oxygen jets. The oxygen jets can be accelerated to supersonic velocities of approximately 2.0 Mach number[1,2] since Laval nozzles can transform high pressure energy into the kinetic energy. However, after the supersonic oxygen jet exits from Laval nozzles, it would be decelerated by mixing with ambient gas, which forms potential core, supersonic core, and subsonic region.[3,4] With the deceleration of supersonic oxygen jets, jets have less momentum which can be transmitted into molten bath. As a result, the mass transfer processes and the reaction rates inside the furnace are depressed. To prolong the length of potential core and improve the stirring effect of supersonic oxygen jets, the coherent jet technology had been applied to EAF steelmaking process.[5,6] The key of this technology is the invention FUHAI LIU and KAI DONG, Doctors, and RONG ZHU, Professor, are with the Beijing Key Laboratory of Research Center of Special Melting and Preparation of High-end Metal Materials, University of Science and Technology Beijing, Beijing 100083, China, and also with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing. Contact e-mail: [email protected] SHAOYAN HU, Doctor, is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing. Manuscript submitted May 3, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
of injector nozzles that deliver shrouding jets with supersonic oxygen jet into the molten bath. The injector nozzles employ oxygen and fuel flame, which shrouds the supersonic jet to prevent it to interact with ambient gas, to maximize the potential core.[7] The shrouding jets retain original diameter and velocity of supersonic jet over long distance, which deliver great amounts of oxygen to liquid melt with less splash and better stirring effect compared to traditional supersonic oxygen lance. The difference between the traditional supersonic oxygen lance and coherent jet oxygen lance is well acknowledged but not fully understood.[8] The coherent jet technology is first proposed by Sarma et al.,[9] and then they showed the fundamental and operating results of this technology. Mahoney[10] analyzed the characteristics of supersonic jets and coherent jets at sub-atmospheric pressure by experimental measurement. Alam et al.[11] reported an experimental research of coherent jets using oxygen and nitrogen as center supersonic jet, which approved the result of numerical simulation analysis. The present study[10–14] only considered the one-step complete combustion between CH4 and O2 in
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