Near-wall fires happen frequently in buildings and may ignite the solids on the wall, leading to a rapid spread of fire. A series of experiments and numerical simulations were conducted on near-wall and free (the same as that of near-wall fire source after mirroring) fires using propane and methane as the fuel to investigate the effect of the wall on flame attachment properties and flame height. The presence of a wall decreases the degree of turbulence for downstream flame and influences the velocity and temperature evolutions due to the no-slip and impermeability conditions. Due to the asymmetric evolution of vortices, intermittent flame attachment emerges at a certain downstream location and is intensified with decreasing fire-wall distance. The upper attachment limit increases with the heat release rate, however, the dependence of the lower attachment limit on the heat release rate is related to the fire-wall distance. The flame attachment probability increases with the aspect ratio of the gap between the fire source and the wall. Grashof number is a suitable parameter to correlate the flame attachment parameters of near-wall fires, including flame attachment limit, length and probability. The flame height increases with decreasing fire-wall distance and is 17.8 %–46.5 % higher than that of free fires. By defining a dimensionless heat release rate incorporating the flame attachment probability, a unified model was built to predict the flame height of near-wall and free fires. The data and models are expected to be useful for evaluating the risk of early-stage near-wall fires.

中文翻译：

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火壁距离对近壁火火焰附着特性和火焰高度的影响


建筑物中经常发生近墙火灾，可能会点燃墙上的固体，导致火势迅速蔓延。以丙烷和甲烷为燃料，对近墙和无火（与镜像后的近墙火源相同）火灾进行了一系列实验和数值模拟，研究了墙体对火焰附着特性和火焰高度的影响。壁的存在降低了下游火焰的湍流程度，并影响了由于无滑移和不渗透条件而导致的速度和温度演变。由于涡流的不对称演变，间歇性火焰附着出现在下游的某个位置，并随着与火墙距离的减小而加剧。附着上限随热释放速率的增加而增大，但附着下限对热释放速率的依赖性与防火墙距离有关。火焰附着概率随火源与墙壁之间间隙的纵横比的增加而增加。格拉斯霍夫数是关联近墙火火焰附着参数的合适参数，包括火焰附着极限、长度和概率。火焰高度随着火墙距离的减小而增加，比自由火高 17.8 %–46.5 %。通过定义包含火焰附着概率的无量纲热释放速率，建立了一个统一的模型来预测近壁和自由火焰的火焰高度。预计这些数据和模型将有助于评估早期近墙火灾的风险。