In the present study, downward flame spread over multiple parallel fuel sheets is investigated experimentally and numerically to understand the mechanism that controls the flame spread process and compare that with the flame spread over a single fuel sheet. A 2D numerical model, based on OpenFOAM is used to simulate the flame spread in a natural convective environment under normal gravity. The model is validated with detailed experimental data involving spatial distributions of temperature and species, and flame spread rates. Flame spread rates on central fuel sheet have been measured in 3 parallel fuel sheets configurations, considering spacing (s) between the fuel sheets in the range of 0.5 cm–3 cm. The flame spread rate varies non-monotonically with spacing, with a peak spread rate at 1 cm spacing between the fuel sheets. Conduction is the dominant mode of heat transfer to the single fuel sheet case. However, in the case of multiple fuel sheets, radiation contributes almost to the same order as that of conduction. The non-monotonic trend in the flame spread rate with spacing is attributed to two opposing effects, namely, increase in oxygen availability and decrease in heat transfer to the fuel, with an increase in the spacing between the fuel sheets.

在本研究中，通过实验和数值研究了火焰在多个平行燃料板上的向下蔓延，以了解控制火焰蔓延过程的机制，并将其与火焰在单个燃料板上的蔓延进行比较。基于 OpenFOAM 的二维数值模型用于模拟正常重力下自然对流环境中的火焰蔓延。该模型通过详细的实验数据进行验证，这些数据包括温度和物种的空间分布以及火焰蔓延速率。考虑到燃料板之间的间距 (s) 在 0.5 cm–3 cm 范围内，已在 3 个平行燃料板配置中测量了中央燃料板的火焰蔓延率。火焰蔓延速率随间距非单调变化，在燃料板之间的 1 cm 间距处具有峰值蔓延速率。传导是向单个燃料板情况下传热的主要方式。然而，在多个燃料板的情况下，辐射的贡献几乎与传导的顺序相同。火焰蔓延速率随间距的非单调趋势归因于两个相反的效应，即随着燃料板间距的增加，氧气可用性的增加和向燃料的传热减少。