A three-dimensional numerical study is performed to investigate concurrent-flow flame spread over thin solid fuels in microgravity. The model considers the burning scenarios of a recently concluded ISS microgravity experiment, Confined Combustion. Cellulose based thin samples are burned in a small flow duct. The height of the flow duct and the radiation reflectance of the duct wall are varied. Flame development and steady spread flame characteristics are compared with the experimental results at various duct heights. The numerical results demonstrate that the confinement imposed by the duct walls accelerates the flow during the combustion thermal expansion, enhancing the conductive heat transfer to the solid samples. When the duct height is below a critical height, the flow confinement limits oxygen supply to the flame, and the duct wall acts as a conductive heat sink. As a result of the interplay of these effects, the flame spread rate and pyrolysis length first increase and then decrease as the duct height decreases. Eventually, the flame fails to spread at a quenching duct height. In addition, side-leading concave (two-teeth fork shaped) flames are observed below the critical duct height. This flame shape increases the flame surface area and facilitates oxygen transport to the combustion zone. When the duct wall reflectance varies, a higher reflectance yields a longer pyrolysis length and a faster spread rate. This is due to enhanced heat input to both the solid sample surface and the gaseous flame. This effect is most significant for medium duct heights. At large duct heights, the duct wall is far from the flame and the sample. At small duct heights, while flame spread rate increases with the wall reflectance, the pyrolysis and flame length remain similar as combustion is limited by oxygen supply.

进行了三维数值研究，以研究微重力下薄固体燃料上的顺流火焰蔓延。该模型考虑了最近结束的国际空间站微重力实验密闭燃烧的燃烧场景。基于纤维素的薄样品在小流道中燃烧。流动管道的高度和管道壁的辐射反射率是变化的。火焰发展和稳定蔓延的火焰特性与不同管道高度的实验结果进行了比较。数值结果表明，管道壁施加的限制在燃烧热膨胀过程中加速了流动，增强了向固体样品的传导热传递。当管道高度低于临界高度时，流动限制会限制对火焰的氧气供应，并且管道壁充当导热散热器。由于这些效应的相互作用，火焰蔓延速率和热解长度随着管道高度的降低先增加然后减少。最终，火焰无法在淬火管道高度处蔓延。此外，在临界管道高度以下观察到侧向凹形（两齿叉形）火焰。这种火焰形状增加了火焰表面积并促进了氧气向燃烧区的输送。当管道壁反射率变化时，较高的反射率会产生更长的热解长度和更快的扩散速度。这是由于对固体样品表面和气态火焰的热输入增强。这种效果对于中等风管高度最为显着。在较大的管道​​高度处，管道壁远离火焰和样品。在较小的管道高度处，