Abstract A numerical investigation is carried out to understand the role of fuel Lewis number ( L e F = α / D F ) on flame spread over thin solid fuel in a quiescent microgravity environment. A three-dimensional numerical model was used wherein fuel Lewis number, LeF was split into directional components along and perpendicular to the fuel surface to elucidate the directional effect of fuel vapor diffusion on flame, spread rate, and its extinction. It is shown that fuel vapor diffusion in the direction perpendicular to the fuel surface plays the most dominant role in the flame spread and extinction behavior. With this approach, the non-monotonic variation of flame spread rate with LeF, influence on limiting oxygen index are also explained. The spreading flame exhibited diffusive-thermal (D-T) instabilities near-extinction. The flame extinguished forming cellular type flame for LeF 1. It is shown that D-T instability induced in one direction triggers the instability in other direction as well. Sensitivity analysis revealed that fuel diffusion becomes increasingly important for narrow fuel strips.

中文翻译：

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燃料路易斯数对微重力条件下薄固体燃料自蔓延火焰蔓延的影响

摘要 进行数值研究以了解燃料路易斯数 (L e F = α / DF ) 在静止微重力环境中对薄固体燃料上火焰蔓延的作用。使用三维数值模型，其中燃料路易斯数，LeF 被分成沿和垂直于燃料表面的方向分量，以阐明燃料蒸汽扩散对火焰、扩散速率及其熄灭的方向性影响。结果表明，垂直于燃料表面方向的燃料蒸汽扩散在火焰蔓延和熄灭行为中起最主要的作用。通过这种方法，还解释了火焰传播速率随 LeF 的非单调变化，以及对极限氧指数的影响。蔓延的火焰表现出接近灭绝的扩散热（DT）不稳定性。LeF 1 的火焰熄灭形成蜂窝式火焰。结果表明，在一个方向上引起的 DT 不稳定性也触发了在另一个方向上的不稳定性。敏感性分析表明，燃料扩散对于窄燃料条变得越来越重要。