Smoke Dynamics from Multiple Fire Sources

What is it about?

This research presents an experimental and numerical study of the smoke dynamics from four fire sources (combined HRR of 5.2MW) with different ignition times and under transient ventilation conditions, inside a 20 m high cubic atrium. Temperature measurements in the plume and close to the walls have been recorded using 59 thermocouples. The data was used in the determination of the smoke layer interface height, with the least-square and the n-percent methods. Results show that significantly worse conditions are induced by multiple sources than those in a single fire of equal power. The results have been obtained using the CFD code FDS (Fire Dynamics Simulator, v6.7.1). The comparison shows that in the far field the temperature predictions are accurate inside the smoke layer (10 m and 15 m) with discrepancies lower than 10%, whereas higher significant discrepancies were observed at the smoke layer interface, i.e. 5 m high, with discrepancies up to 20%. The analysis confirmed the applicability of FDS to the assessment of the smoke dynamics under complex fire conditions away from flames together with the importance of considering fires with multiple sources due to the faster smoke production compared with single fires.

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Photo by Guido Jansen on Unsplash

Photo by Guido Jansen on Unsplash

Why is it important?

When a fire starts in an enclosure, the fuel configuration allows for it and safety systems do not control the fire (in this case suppression, and to some extent smoke control). Thus, it is likely that subsequent fire sources may be ignited, generating multiple fires that will finally contribute to the overall fire. A typical case of such fires occur in large car parks (Tohir et al., 2018), or industrial scenarios (Shafee and Yozgatligil, 2018). Moreover, consideration of more than one fire source is more common in the design of road tunnels (Zhao et al., 2019), (K. He et al., 2019), which show significantly different evolution to that of a single fire. Similar fire behavior can be anticipated in large open plan compartments, such as shopping malls or warehouses in which large, individual sources of fire can be found – such as shops with upholstered furniture, beds and mattresses; and during holiday events where series of makeshift houses are built to form a “market” setting. A spread of fire in such a scenario can be an effect of either heat radiation and/or direct flame contact. In that regard, recent works have addressed some of these effects, such as that by (Wan et al., 2019) on the radiative heat transfer from multiple fire sources or those by (Weng et al., 2004), and (P. He et al., 2019) on merging effects of fire plumes.

Perspectives