Abstract This article reports Large Eddy Simulation (LES) of 30 cm diameter methanol pool fires in order to investigate the effects of the burner boundary conditions on the pool dynamics. The numerical model involves state-of-the-art subgrid scale (SGS) sub-models for mixing, combustion and turbulence-radiation interaction with all the model constants computed dynamically. The non-adiabatic steady laminar flamelet (SLF)/presumed filtered density function (FDF) combustion model is used whereas the radiation model combines the Rank Correlated Full Spectrum k-distribution (RCFSK) for spectral radiation with the finite volume method (FVM) as radiative transfer equation (RTE) solver. The baseline case considers a burner located one-pool diameter above the floor and a fuel lip height of 1 cm as specified in the experiments used for model validation. Model predictions for puffing frequency, mean and rms temperature and velocity, mean molar fractions of major species, radiative loss to the surrounding and radiative and total heat feedback to the fuel surface are in good agreement with the available experimental data. Two other burner boundary conditions are designed. The first disregards the fuel lip height while keeping the burner located one-pool diameter above the floor. The second modifies the first configuration by assuming that the burner rim is floor flush. Model results show that the burner boundary conditions affect significantly the flow structure and the pool fire dynamics by altering the flame base instability near the edge of the pan. A non-zero fuel lip height produces significantly wider and shorter flames which affect the heat feedback toward the fuel surface whereas altering the air entrainment at the pool basis enhances substantially the puffing frequency. This shows that the experimental burner boundary conditions have to be reproduced scrupulously for relevant model validations.

中文翻译：

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中型甲醇池火灾的大涡模拟——池边界条件的影响

摘要 本文报告了直径 30 cm 甲醇池火灾的大涡模拟 (LES)，以研究燃烧器边界条件对池动力学的影响。数值模型包括最先进的子网格尺度 (SGS) 子模型，用于混合、燃烧和湍流-辐射相互作用，所有模型常数都是动态计算的。使用非绝热稳定层流火焰 (SLF)/假定过滤密度函数 (FDF) 燃烧模型，而辐射模型将光谱辐射的秩相关全谱 k 分布 (RCFSK) 与有限体积法 (FVM) 结合为辐射传递方程 (RTE) 求解器。基准案例考虑了燃烧器位于地板上方一池直径和 1 厘米的燃料唇高度，如用于模型验证的实验中指定的那样。对喷气频率、平均和均方根温度和速度、主要物质的平均摩尔分数、对周围的辐射损失以及对燃料表面的辐射和总热反馈的模型预测与可用的实验数据非常一致。设计了另外两个燃烧器边界条件。第一个忽略燃料唇的高度，同时保持燃烧器位于地板上方一个水池直径的位置。第二个通过假设燃烧器边缘与地板齐平来修改第一个配置。模型结果表明，燃烧器边界条件通过改变锅边缘附近的火焰底部不稳定性，显着影响流动结构和池火动力学。非零燃料唇高度会产生明显更宽和更短的火焰，这会影响向燃料表面的热反馈，而改变水池基础上的空气夹带会显着提高喷气频率。这表明必须仔细复制实验燃烧器边界条件以进行相关模型验证。