PRESENTATION - 22
Analysis of Waves in a Cavity and their Significance to Splashing in
Steelmaking
Shabnam Sabah, Geoffrey Brooks, Jamal Naser
Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
Email: ssabah@swin.edu.au
In steelmaking, metal droplets are generated due to the impact of supersonic jets onto the
liquid metal bath. This phenomenon is generally referred to “splashing” [1]. Splashing is an
important phenomenon as it provides large interfacial area between reacting phases and
promotes high overall reaction rates. Dogan et al. [2] estimated that 60% of decarburization
in steelmaking process takes place in the gas-metal-slag emulsion phase during the main
blow. Therefore, it is important to understand droplet generation if we are to optimize
steelmaking processes.
In literature only a few works [3,4] discuss the formation of waves in the cavity. But there is
lack of understanding how waves inside the cavity affect splashing. In the present work, a
1/10th cold model of oxygen steelmaking was used to study wave phenomenon in the cavity
and how its characteristics vary with the changing momentum of impact jet and thereby
affecting splashing. Compressed air was passed through a top straight nozzle. Water was used
to simulate liquid steel. As the first phase of the investigation, the slag phase was not
included in this study. A transparent cylindrical rig, made of perspex sheet was used as the
vessel. A high speed camera (MotionPro Y, model Y4L (1024x1024 – 4000 fps)) was used to
take photos of the cavity and the splashing at a rate of 30 frames/ second for a time duration
of 4 minutes. In addition, a video of 2 second was taken at 2000 frames/ second rate in order
to observe the droplet generation process.
(a)
(b)
Figure 1: (a) Peregrine sheet [5]; (b) sheet structure at flow rate 50 L/min, lance height 150
mm
As air jet hit the water surface, it created waves inside the cavity. These waves were pushed
towards the edge of the cavity by deflected gas flow. At the edge of the cavity, these waves
grew to certain critical amplitudes. These waves were like sheets structure at the edge of
cavity. They were similar to “peregrine sheet” described in the general splashing literature
[5]. Figure 1(a) and (b) shows an irregular peregrine sheet from an earlier study and a typical
sheet structure observed in the cold modeling experiment respectively.
High Temperature Processing Symposium 2013
Swinburne University of Technology
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From high speed video, droplet formation process was observed and three stages could be
identified- amplitude of the waves (which will be called “sheets” from now on) enlarged at
the edge of the cavity, instability grew formed at the rim of the sheets and fingers were
formed and finally, fingers broke up into one or number of droplets. Depending upon lance
height and air flow rate, any one or two or all three stages were found. For example, at gas
flow rate 40 L/min and lance height 150 mm, only sheet structures were observed. As gas
flow rate increased from 40 L/min to 50 L/min, fingers as well as droplet generation began. It
was observed that frequency and amplitude of the waves in the cavity, the height of the sheets
increased as gas momentum on bath surface increased which ultimately, increased droplet
generation. Also, the shape of the droplets changed from circular to irregular shapes as
momentum of impact jet grew.
It was found that the characteristics of the waves have an effect on the splashing droplet
amount and shape. A variety of mathematical techniques (including Fast Fourier Analysis)
were used to analyze the wave behavior and the results from this analysis will be discussed at
the symposium.
References
1. Tago Y. and Y. Higuchi, Fluid flow analysis of jets from nozzles in top blown process.
ISIJ International, 2003. 43(2): p. 209-215.
2. Dogan, N., G.A. Brooks, and M.A. Rhamdhani, Comprehensive Model of Oxygen
Steelmaking Part 3: Decarburization in Impact Zone. ISIJ International, 2011. 51(7): p.
1102-1109
3. Peaslee, K.D. and D.G.C. Robertson. Model studies of splash, waves, and recirculating
flows within steelmaking furnaces. in Steelmaking Conference Proceedings. 1994.
Warrendale, PA: Iron & Steel Society 77: p. 713-722.
4. Lee, M., V. Whitney, and N. Molloy, Jet-liquid interaction in a steelmaking electric arc
furnace. Scandinavian Journal of Metallurgy, 2008. 30(5): p. 330–336.
5. Deegan, R., P. Brunet, and J. Eggers, Complexities of splashing. Nonlinearity, 2008. 21:
p. C1.
High Temperature Processing Symposium 2013
Swinburne University of Technology
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