FORMATION MECHANISM AND INFLUENCE FACTORS OF SINK VORTEX DURINGLADLE TEEMING

Haiyan TANG^{1,}^{2}(),Yongchang LIANG^{2}

1 State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China 2 School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

To investigate the formation mechanism of sink vortex during ladle teeming, the effects of some factors such as Coriolis force, the position of the ladle shroud and initial tangential velocity of the fluid on the vortex formation process have been studied using numerical simulation combined with experiments. In addition, the evolution tendencies of tangential and radial velocities of the fluid over radial position were studied at certain initial tangential velocity. The results show that as for fully settled fluid, Coriolis force is the major reason for sink vortex formation and the spinor near the shroud is the initial driving force. There is no obvious effect of the ladle shroud position on the critical height of vortex for fully settled fluid, while the critical height of vortex significantly decreases with increasing shroud eccentricity for the fluid with a certain initial velocity, and the tangential motion is the main driving force for vortex formation in this case. The initial tangential velocity affects the critical height significantly. The larger the initial angular velocity is, the earlier vortex occurs and the bigger the critical height of vortex is. As a result, keeping the fluid settled for some time is an effective measure to delay vortex during ladle teeming. The relationship between the start height of vortex (H_{SS}) and initial angular velocity (ω) can be expressed as H_{SS}=0.11+2.85ω-4.04ω^{2}+1.95ω^{3}, and that of the height of air column extending to shroud (H_{CS}) and ω expressed as H_{CS}=0.09+1.49ω-0.79ω^{2}, both of the fitting degrees are higher than 0.99.

Fund: Supported by National Natural Science Foundation of China (No.51374021), Fundamental Research Funds for the Central Universities (No.06102110) and Research and Development Funds of State Key Laboratory of Advanced Metallurgy (No.41603014)

Fig.1 Schematic of meshing division of ladle model

Fig.2 Schematic of experimental set-up

Fig.3 Schematics of sink vortex at different stages during ladle teeming (H_{SS}—vortex starting height, H_{CS}—height of air column penetrating shroud, H_{DS}— height of strong air entrapment occurring)

Fig.4 Comparison of the critical heights of strong air-entrapment vortexes between the simulated and experimental results with different diameters of shroud

Fig.5 Comparisons of the critical heights of vortexes without (a) and with (b) Coriolis force

Fig.6 Diagrams of velocity vectors without (a) and with (b) Coriolis force at cross-section of 80.0 mm when liquid level reaching 82.0 mm

Fig.7 Diagrams of velocity vectors without (a) and with (b) Coriolis force at cross-sections of different heights when liquid level reaching 350.0 mm

Fig.8 Effects of eccentricity on the critical heights of vortexes at initial tangential velocity ω=0 rad/s (a) and 0.2 rad/s (b)

Fig.9 Effects of the initial tangential velocity (ω) on critical height of vortex at absolute height (a) and non-dimensional height (b)

Fig.10 Tangential velocity distributions along radial positions at different liquid levels and ω=0 rad/s (a), 0.2 rad/s (b), 0.4 rad/s (c), 0.6 rad/s (d), 0.8 rad/s (e) and 1.0 rad/s (f)

Fig.11 Radial velocity distribution along radial position when the liquid surface decreasing to different heights with ω=0 and 0.2 rad/s (Initial level is 400.0 mm. Negative values represent fluid flowing to center while positive ones off center)

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