open access

https://hdl.handle.net/2115/95853

Identifying two ignition modes of polymer insulated wires with continuous excess current in microgravity

英語

Fire safety in space

2023-12

Elsevier

Fire safety journal

141

103925

Overload ignition of electric wires in microgravity has been investigated for space fire safety. Microgravity experiments from drop towers and parabolic flight have been conducted to observe the overall ignition phenomena. Two-dimensional numerical simulations were performed employing finite-rate chemistries in both condensed and gas phases. As the applied current changes, two distinct ignition modes were found in both experiments and simulations, one away from the wire and the other near the wire surface, named "spontaneous ignition" and "wire assisted ignition", respectively. After validating ignition delay times by experiments, the simulation results were used to discuss the transition of two ignition modes. With a lower current, the spontaneous exothermic reaction at the pyrolysis gas front led to the far-distance ignition. While with a higher current, the local heat loss suppressed spontaneous ignition; meanwhile, the excessive heat from the exposed core wire caused the surface ignition. In addition, the ignition energy showed a non-monotonical increase with the applied current, where the minimum ignition energy was consumed with 5.5 A current supply implying the high fire risk of the "spontaneous ignition" regime. The control mechanisms of the ignition energy change in different stages were discussed.

学術雑誌論文

Accepted Manuscript

Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International

© [2023]. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

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