Effect of Nozzle Exit Wear on the Fluid Flow Characteristics of Supersonic Oxygen Lance
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THE oxygen lance is one of the key devices in converter steelmaking. Its main function is to convert the low-flow-rate oxygen in the inner tube of the oxygen lance into a supersonic jet through the shrinkage-expansion Laval nozzle of the oxygen lance, such that the oxygen can fully come into contact with the molten pool and provide good dynamic conditions for decarburization, dephosphorization, and temperature rise during converter smelting. Based on their different manufacturing methods, the production forms of oxygen lance nozzles are mainly divided into casting and forging. The service life of nozzle produced by casting method is generally 100 to 300 times, and the service life of nozzle produced by forging method is generally 300 to 600 times. Casting nozzles are mostly used in converters whose capacity is less than 150 t, while CHAO FENG, BAOCHEN HAN, LIUJIE YAO, WENHE WU, JUANJUAN JIANG, SHAOYAN HU, and JIANFENG DONG are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. RONG ZHU and GUANGSHENG WEI are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing and also 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. Contact e-mails: [email protected], [email protected]. Manuscript submitted May 13, 2019.
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forging nozzles are mostly applied in 100–350 t converters. With the increase in the number of smelting furnaces, the nozzle exit of the oxygen lance would be corroded to varying degrees because of the scouring effect of the high-speed oxygen jet at the steelmaking temperature. As a result, the operating conditions of the oxygen lance have deviated from the design parameters, and the jet characteristics have also changed. Presently, most studies regarding the supply of supersonic oxygen in converter steelmaking are mainly focused on the jet behavior of the oxygen lance with the designed structure, wear mechanism of the nozzle exit, and metallurgical effects in industrial application.[1–7] Furthermore, many computational fluid dynamics (CFD) models of various types of oxygen lances have been developed and validated by jet testing experiments.[8–16] Li et al.[17] studied the effects of different operating pressures, nozzle angles, and ambient temperatures on the jet behavior of the oxygen lance and found that with decreasing nozzle angle and increasing number of nozzles, each jet was easy to coalesce. Moreover, the higher ambient temperature could delay jet attenuation and promote the expansion of the jet boundary, which was beneficial to increasing the impact area and depth of the molten pool. Similar results were also obtained and reported by Wang et al.[18] Yang et al.[19] carried out 1:10 water model experiments using different air flow rates and nozzle parameters. The results showed that the two-angle sta
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