Swirl Motion of Bubbling Jet

Fig. 5.6 Classification of the swirl motions of bubbling jet in a cylindrical vessel...

Iguchi M, Hosohara S, Kondoh T, Itoh Y, Morita Z (1994) Effects of the swirl motion of bubbling jet on the transport phenomena in a bottom blown bath. ISIJ Int 34 330-337... 

The radial distributions of gas holdup, a, measured by Iguchi et al. [24] at four representative axial positions are shown in Fig. 2.8. The a distribution at z = 1.5 cm is very steep near the centerline of the bubbling jet. Two peaks appeared in the a distributions measured at z = 4.0 and 7.0cm. These two peaks are not caused by the swirl motion of a bubbling jet because no swirl motion was observed under the... 

Swirl motion of a bubbling jet can be classified into two, as shown in Fig. 5.6. One occurs when the bath depth //l is smaller than the bath diameter D. The radial... 

The contribution of the kinematic viscosity of liquid, vl, was found to be very small and negligible. This result implies that a bath subjected to swirl motion of a bubbling jet is primarily mixed by the strong wave motions induced by the swirl because the wave motions are not affected by the kinematic viscosity of the liquid. 

Swirl motion of a bubbling jet occurs even in the presence of a thin slag layer on a molten metal layer. The bath surface oscillations, however, are strongly modulated compared with those in the absence of the slag layer. This section presents the effects of the top slag layer on the first kind of swirl motion of a bubbling jet and the behavior of the slag layer. 

The starting time, Ts s, is defined as the time duration from the start of gas injection to the moment at which the swirl motion of a bubbling jet reaches steady state. It is one of the important parameters used for the design of metallurgical processes. The thickness of the upper silicone oil layer lengthens the starting time, as shown in Figs. 5.49 and 5.50. Note that has a minimum at the aspect ratio of approximately 0.5 (//l = 10 cm). 

Figures 5.51 and 5.52 show that the swirl period of a bubbling jet is not sensitive to the existence of the upper silicone oil layer. This trend is irrespective of whether the swirl motion of the layer is classified into Types 2 and 3.

Iguchi M, Hosohara S, Koga T, Yamaguchi R, MoritaZ (1992) The swirl motion of vertical bubbling jet in a cylindrical vessel. Tetsu-to-Hagane 78 1778-1785... 

In this section, swirl motions, i.e., tangential oscillation modes of a bubbling jet in a cylindrical bath with centric bottom gas injection are described. The oscillations are classified into two categories and empirical correlations are presented for the critical bath depths for the initiation and cessation of swirl motion and the swirl period. 

A variety of swirl motions are known to occur in a bath agitated by gas injection when the bath surface is exposed to the atmosphere, as described in Sect. 5.2.1.4 [18,23, 29-37]. In particular, two types of swirl motions typically occur in a circular cylindrical bath agitated by single-nozzle bottom gas injection, as schematically illustrated in Fig. 5.6 [29, 30] One is observed over an aspect ratio, H /D, from approximately 0.2-1.0. The other appears for H /D > 2. No swirl motion occurs when the aspect ratio falls in the range of 1.0-2.0. The former swirl motion is caused by bath surface oscillations due to quasi-periodic generation and subsequent arrival of bubbles at the bath surface. It resembles the rotary sloshing of a water bath contained in a circular cylindrical vessel [16,17,38]. The latter is caused by the Coanda effect [26], which appears when a bubbling jet approaches the side wall of the vessel [29,30,39]. 

The motions of the slag layer were classified into three categories, as shown in Figs. 5.47a-c. When the gas flow rate gg was lower than a certain critical value, the first kind of swirl motion was not observed (Fig. 5.47a). When gg exceeded the critical value, the slag layer disintegrated into small droplets (reverse emulsification). On average, the droplets did not rotate around the vessel axis, i.e., they remained at their initial position, but the bubbling jet rotated in the plume eye (Fig. 5.47b). 

---