地下煤火蔓延模型与机制研究对我国煤炭资源绿色安全开采具有重要意义。目前地下煤火阴燃正向蔓延模型主要存在问题：简化的煤燃烧单步反应忽略了水分蒸发和热解吸热反应对蔓延的重要影响作用；缺乏实验数据验证模型的有效性。为此，构建了包含水分蒸发、煤热解和碳氧化三步反应体系的地下煤火阴燃正向蔓延数学模型；采用COMSOL Multiphysics有限元软件数值计算了该理论模型；开展了不同地裂缝渗透性条件下热浮力驱动地下煤火阴燃正向蔓延实验，进行对比实验和数值计算。结果表明：构建的模型揭示了地下煤火阴燃蔓延供氧控制机制，不仅能预测地下煤火阴燃正向蔓延高温区域的温度和蔓延速率，而且还能合理地预测阴燃多步反应速率以及氧气、煤、碳和灰分质量分数的时空演化。

Modeling and understanding of underground coal fire is of significance for green-and-safe mining of coal resources in China. Two issues remain unsolved in forward-propagation models of underground coal smoldering fires: one-step coal oxidation has been too simple so that endothermic reactions such as water evaporation and pyrolysis that have important influence on smoldering propagation of underground coal fires have been not considered; and models have not been validated via experimental data. In this work, a three-step chemical reaction scheme including water evaporation, coal pyrolysis, and char oxidation was employed and mathematic model in terms of forward propagation of underground coal smoldering fires was established. The theoretical model was numerically calculated using COMSOL Multiphysics finite element software. The theoretical model was numerically calculated using COMSOL Multiphysics finite element software, and the forward smoldering spread experiment of underground coal fire driven by thermal buoyancy under different ground crack permeability conditions was carried out. Comparison experiment and numerical calculation were carried out. Results show that the proposed model not only owns good capability to predict the peak temperature and velocity of smoldering propagation of underground coal fire, but also can inversely plot multiple step chemical reactions as well as spatiotemporal evolutions of oxygen and solid species mass fractions. In addition, the controlling mechanism of smoldering propagation of underground coal fires was further revealed.