Smoldering Fire of High-Density Cotton Bale Under Concurrent Wind

Cotton is the most widely used natural textile fiber for human beings, and fire safety during transportation, storage, and manufacturing is of great significance. This work investigated the smoldering burning of a high-density cotton bale (36 L and 225 kg/m³) tightened by thin steel wire ropes under the concurrent wind. Without wind, the creeping smoldering spread showed two stages: (I) the relatively fast surface spread until the smoldering front covered the entire free surface (13 cm/h), and then (II) the slow in-depth spread from the surface to the internal (4 cm/h). With a concurrent wind, only one major concurrent smoldering front was observed from the free surface to the internal fuel, where the rate of smoldering spread decreased as the sample depth increased. The smoldering spread rate and peak temperature were found to increase almost linearly with the wind velocity due to the enhanced oxygen supply. The steel wire rope could appreciably obstruct the free-surface spread and slow down the overall smoldering spread. A large wind occasionally led to a smoldering-to-flaming transition, but the flame could not be sustained. This research improves our understanding of the wind effect on the smoldering spread in the compressed porous biomass and helps evaluate the fire risk of cotton during transportation and storage.