工程科学学报 (Dec 2018)
Numerical simulation research on flow fields in combined blown converter at steelmaking temperature
Abstract
Top and bottom combined blown converter has been widely utilized in steelmaking process.Multiple supersonic oxygen jets generated by top blown oxygen lance penetrate into the molten bath and form a penetration cavity on the surface of molten bath, which is the main reaction zone in steelmaking.Therefore, the characteristics of the multiple oxygen jets play a crucial role in converter flow fields and metallurgical performance.Several numerical and experimental studies have been conducted previously to investigate the supersonic oxygen jet.However, most of them were carried out at ambient room temperature by ignoring the high-temperature environment in steelmaking converters.In fact, the characteristics of supersonic oxygen jet are closely related to the ambient temperature.The effect of ambient temperature on single-stream oxygen jet has been previously studied, and it was confirmed that the jet characteristics improve with the increase in ambient temperature.Characteristics of multiple jets generated by converter oxygen lance at high ambient temperatures have not been previously studied.There are big differences between single-stream oxygen jet and multiple jets because the multiple jets deviate from the axis of oxygen lance.The coalescence phenomenon occurs in these multiple jets due to formation of low pressure zone between them.The difference between multiple jets characteristics at ambient room temperature and ambient steelmaking temperature inevitably leads to the difference between penetration cavity and flow fields in the converter, which has never been studied.To reveal the multiple jets characteristics and jet-bath interactions in converters at steelmaking temperature, a three-dimensional fullscale geometric model based on an industrial 110 t combined blown converter was established in this work.Using the combined blown converter model, coupled with standard k-epsilon turbulence model and volume of fraction multiphase model, the effect of ambient temperature on multiple oxygen jet characteristics was studied in detail.Moreover, jet-bath interactions at room temperature and steelmaking temperature were compared and analyzed.The results show that with the increase of ambient temperature, velocity attenuation of the multiple jets is inhibited and the radial expansion of the jets is aggravated.Meanwhile, the multiple jets are heated by the ambient medium, and the final temperature of multiple jets becomes close to ambient temperature, which decreases the jet density.Coalescence between multiple jets is suppressed in high ambient temperature.Research on the jet-bath interactions shows that penetration depth and flow velocity in molten bath are larger at steelmaking temperature because the velocity attenuation of supersonic jet is suppressed.These results indicate that the effect of ambient temperature in multiphase numerical researches is significant and cannot be ignored.
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