This study presents the results of a comprehensive experimental investigation and numerical simulation of the downward flame spread over PMMA slabs. For the first time, in the case of downward flame spread over PMMA slab 9.6 mm thick, temperature and species concentration fields in the gas-phase flame, temperature profiles in the condensed phase and dependence of the heat flux to the burning surface on the distance from the flame front were obtained. A coupled model of heat and mass transfer involving two-dimensional elliptic conservation equations both for gas phase and solid fuel has been used with the fuel surface approximation of the samples burnout. This allowed us to state, for the indefinite intermediate mode (in terms of the sample thickness, which are not neither thermally thin nor thermally thick), a mathematical model ensuring good agreement between the experimental and calculated macro parameters of combustion. The results of comparing the experimental and calculated data allowed us to determine a number of facts, which, despite the satisfactory agreement between the simulation and the experimental data in the main macro parameters, indicate the necessity of further improvement of the model derived. Such facts are: the increasing disagreement between the calculation and the experiment in the position of the maxima of the temperature in the gas phase as the distance from the flame front grows; essential difference in the width of the MMA and O₂ consumption zone between the calculation and the experiment; identification in the experiment of CO as an intermediate product. Further improvement of the model should be aimed at more detailed development of the combustion reaction mechanism, which should consider at least two steps.

这项研究提出了对PMMA平板向下火焰蔓延进行全面实验研究和数值模拟的结果。第一次，在火焰向下散布在9.6毫米厚的PMMA平板上的情况下，气相火焰中的温度和物质浓度场，凝结相中的温度分布以及到燃烧表面的热通量对距离的依赖性从火焰前沿获得。包含二维气相和固体燃料椭圆守恒方程的传热和传质耦合模型已与样品燃尽的燃料表面近似一起使用。这使我们可以针对不确定的中间模式（就样品厚度而言，既不热也不热）进行陈述，一个数学模型，可确保燃烧的实验参数和计算的宏观参数之间具有良好的一致性。通过对实验数据和计算数据进行比较的结果，我们可以确定许多事实，尽管仿真和实验数据在主要的宏观参数之间达成了令人满意的一致性，但仍表明有必要进一步改进派生模型的必要性。这些事实是：随着距火焰前沿距离的增加，气相最高温度位置的计算与实验之间的分歧越来越大；MMA和O的宽度的本质区别 尽管仿真和实验数据在主要的宏观参数中令人满意地吻合，但表明有必要进一步改进导出的模型。这些事实是：随着距火焰前沿距离的增加，气相最高温度位置的计算与实验之间的分歧越来越大；MMA和O的宽度的本质区别 尽管仿真和实验数据在主要的宏观参数之间令人满意地吻合，但表明有必要进一步改进导出的模型。这些事实是：随着距火焰前沿距离的增加，气相最高温度位置的计算与实验之间的分歧越来越大；MMA和O的宽度的本质区别在计算和实验之间有_2个消耗区；在实验中将一氧化碳鉴定为中间产物。该模型的进一步改进应着眼于燃烧反应机理的更详细发展，该燃烧反应机理应考虑至少两个步骤。