Moderate micro-explosion during the combustion of iron wire in atmospheric air |
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| Institution: | 1. Simulation of Reactive Thermo-Fluid Systems, TU Darmstadt, Otto-Berndt-Straße 2, Darmstadt 64287, Germany;2. Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven 5600 MB, the Netherlands;3. Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal H3A0C3, Canada;1. Key Lab of Education Ministry for Power Machinery and Engineering, School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China;2. Division of Combustion Physics, Lund University, P.O. BOX 118, S-221 00 Lund, Sweden;3. Department of Energy Science, Lund University, 221 00 Lund, Sweden;1. Department of Natural Sciences, The Open University of Israel, 4353701 Raanana, Israel;2. EMPI, Institute for Energy and Materials Processes – Reactive Fluids, University of Duisburg-Essen, 47048 Duisburg, Germany;3. EMPI, Institute for Energy and Materials Processes – Fluid Dynamics University of Duisburg-Essen, 47048 Duisburg, Germany;4. CENIDE, Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, 47048 Duisburg, Germany;5. School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv, Israel;6. Faculty of Chemistry, Theoretical Chemistry, University of Duisburg-Essen, 45141 Essen, Germany |
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| Abstract: | The combustion of a thin iron wire in atmospheric air was investigated through the in-situ high-speed videography and the sampled product characterization. During the iron wire burning, a hot spherical ball was found to form at the wire tip and propagate with a speed of around 3.5 cm/s along the wire. Meanwhile, small bright droplets were randomly ejected from the burning ball. In fact, the burning spherical ball is hollow to be a ferric bubble according to the SEM image of sampled product. The high-speed videography further indicates that the small droplet ejection occurs largely owing to the bubble bursting, that is called the moderate micro-explosion to be different from the conventional micro-explosion process. For this bubble bursting process, the volume expansion rate inside the burning bubble needs not to be very fast but the bubble size should be adequate. If the bubble is too small (e.g. <50 μm), the droplet ejection during bubble bursting may be difficult to occur. Furthermore, the bubble formation is mainly attributed to the fact that carbon dissolved in iron can be preferentially oxidized to produce CO2, which nucleates to generate a large bubble inside the ferric ball. It is noted that less than 0.05%wt of carbon content is enough for the bubble formation. It thereby suggests that carbon content should be accurately measured to predict the micro-explosion phenomena during iron combustion. |
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