Dynamics of the spout of gas plumes discharging from a melt: Experimental investigation with a large-scale water model
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I. INTRODUCTION
II. EXPERIMENTAL METHOD
MANY investigations have been carried out on the characteristics of gas plumes in liquids, but most of them refer to the bulk of the liquid or bulk of the liquid/gas region. The surface where the gas is discharged to the surrounding atmosphere is called the spout. This part of the system has received little attention,[1–8] although it has considerable significance. The spout region is the most important site, in a ladle or ladle furnace, for the slag/metal reactions, and it is the site for the undesired side reactions with air. In two preceding articles, we have studied the size of spout eyes[7] and the elevation of the spout over the meniscus at rest.[8] “Spout eyes” are those parts of the spout which are uncovered by slag and develop at high gas flow rates. The previous investigation of the spout height[7] was carried out on a cold model involving mercury as the liquid and on real steel ladles of 120 and 350 t in size. The spout is highly dynamic. It wanders laterally, and its momentary height profile is irregular and fluctuates. These effects have to be taken into account in the selection of measuring techniques, and they require clear definitions of the quantities to be measured. It was found in the previous study[8] that the momentary maximum values of spout height were rather close to each other in the mercury model and in the real steel ladle, if expressed nondimensionally. However, the model experiments could be carried out only with a small (29 cm i.d.) vessel, so that the difference in geometry (and gas flow rate) to the real system is large. Particularly, more data on the specifics of the dynamics of the phenomenon are needed, which can hardly be obtained on the real system. It was decided, therefore, to carry out an additional investigation on the spout formation with a water model of pilot scale.
The cylindrical vessel is the same as that used previously[9] (Figure 1). The size is that of a 35 t steel ladle. Its i.d. is 160 cm, and the water height is 180 cm at rest. The air was injected at the center of the vessel through a nozzle, which had its end flush with the bottom of the vessel. The system has been described in detail elsewhere.[9] Two effects were investigated: the lateral wandering of the spout and the spout height.
A. Lateral Wandering of the Spout on the Water Bath The lateral wandering of the spout increases with the size of the vessel and, therefore, it is much more pronounced in the large water basin than in the small mercury bath. It was measured with a video technique[7] (Figure 1) by observing the spout area with a charge-coupled device camera, combined with data evaluation by a processing system. A ring lamp was used to obtain cylindrically symmetrical illumination of the water surface. The pictures were stored during the experiment and were treated afterward first by marking the differently reflecting zones with different colors, then by determining the center of gravity of the central area of the spout. Two types of experiments were carri
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