Abstract The Michigan State University Narrow Channel Apparatus (MSU-NCA) was used to investigate opposed flow flame spread over samples of thermally thick Polymethylmethacrylate (PMMA). Three different fuel thicknesses were tested for mean airflow velocities 8-58 cm/s. The sample thicknesses were 6.6 mm, 12.1 mm and 24.5 mm, respectively. The measured flame position versus time determined the spread rate. Flame spread rates ranged between 0.02 - 0.07 mm/s depending on fuel thickness and mean opposed flow. Complete sample burnout occurred for the 6.6 mm and 12.1 mm samples at the critical flow velocity of 30 cm/s ± 5 cm/s and higher. The flame spread results appeared to be independent of flow velocities for this range (>30 cm/s): this plateau regime is identified as the regressive burning regime. The 24.5 mm thick samples never completely burned through, but they entered the regressive burning regime at 41.4 cm/s flow velocity. The nature of surface regression and its influence on the spread mechanism in this regime at high flow velocities was discussed for completely burned through samples (6.6 mm and 12.1 mm) and partially burned through samples (24.5 mm). For 12.1 mm thick samples, the flame spread results were compared with the same material (PMMA) and similar thickness (12.7 mm) results from the 1981 Fernandez-Pello et al. study. Their tests used a wind tunnel having a different length and cross-section than the MSU-NCA. The comparison was favorable when employing the stretch rate theory of flame spread incorporating the appropriate numerically computed stretch rate. Since buoyancy was an important factor in the 1981 study, when the buoyant stretch was also included, excellent agreement was obtained between the Fernandez-Pello et al. data and the current NCA data. The results demonstrated the effectiveness of the stretch rate theory for markedly different experimental configurations.

中文翻译：

---

对流火焰在热厚固体燃料上蔓延：浮力流动抑制、拉伸率理论和回归燃烧状态

摘要 密歇根州立大学窄通道装置 (MSU-NCA) 用于研究在热稠聚甲基丙烯酸甲酯 (PMMA) 样品上的对流火焰蔓延。针对平均气流速度 8-58 cm/s 测试了三种不同的燃料厚度。样品厚度分别为 6.6 毫米、12.1 毫米和 24.5 毫米。测量的火焰位置与时间的关系决定了蔓延速度。火焰蔓延速度在 0.02 - 0.07 毫米/秒之间，具体取决于燃料厚度和平均对流。6.6 mm 和 12.1 mm 样品在临界流速为 30 cm/s ± 5 cm/s 或更高时发生完全样品烧毁。火焰蔓延结果似乎与此范围内的流速无关 (>30 cm/s)：该平台状态被确定为回归燃烧状态。24. 5 毫米厚的样品从未完全烧透，但它们以 41.4 厘米/秒的流速进入了回归燃烧状态。针对完全烧穿的样品（6.6 毫米和 12.1 毫米）和部分烧穿的样品（24.5 毫米）讨论了表面回归的性质及其在高流速下对这种情况下扩散机制的影响。对于 12.1 毫米厚的样品，火焰蔓延结果与来自 1981 年 Fernandez-Pello 等人的相同材料 (PMMA) 和相似厚度 (12.7 mm) 的结果进行了比较。学习。他们的测试使用了长度和横截面与 MSU-NCA 不同的风洞。当采用结合适当的数值计算的拉伸速率的火焰蔓延拉伸速率理论时，这种比较是有利的。由于浮力是 1981 年研究中的一个重要因素，当还包括浮力拉伸时，Fernandez-Pello 等人之间获得了极好的一致性。数据和当前的 NCA 数据。结果证明了拉伸速率理论对于明显不同的实验配置的有效性。