Abstract A series of experimental tests were conducted in a narrow obstructed channel to investigate the influence of obstacle distribution mode (unilateral and bilaterally symmetrical distribution) and obstacle aspect ratio (the width-to-height ratio in flame propagation direction) on vapor deflagration. Rectangular obstacles with different aspect ratios 0.9–2.1 were used. The flame propagation speed, flame front structure, overpressure and local temperature near obstacles were recorded and analyzed. The results indicated that different obstacle distribution modes would not fundamentally alter the propagation mechanism of deflagration flame and overpressure. The shear action of obstacle edges and the confined space structural form between the obstacle and the channel boundaries both exerted a significant effect on deflagration flame propagation. And two acceleration stages existed in the deflagration, and the flame speed peaks appeared above obstacle and near the channel portal, respectively. Specifically, when aspect ratio was 1.8, the maximum flame speed peaked to 102.5 m/s. Moreover, obstacle aspect ratio has shown a significant influence on flame front, and the flame front structure experienced complex changes as it passed through obstacle. What's more, an interesting reverse flame phenomenon was observed, which resulted in a larger area of violent flame combustion. The maximum length of reverse flame decreased firstly and then increased with the increase of obstacle aspect ratio, which probably ascribed to the inertial force of fluid. Accordingly, a simple empirical equation was proposed to predict the reverse flame length during flame propagation in the narrow obstructed channel. This equation performs well in prediction of reverse flame length in current application range. Meanwhile, the local temperature peak is closely related to the local deflagration reaction intensity affected by obstacle aspect ratio. In addition, it is also found that the deflagration overpressure and flame propagation involved the obvious coupling mechanism. Deflagration overpressure and flame speed reached peaks almost simultaneously. This coupling mechanism could significantly expend the impact range of deflagration.

中文翻译：

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障碍物纵横比对窄通道乙醇液体蒸汽爆燃影响的实验研究

摘要 为研究障碍物分布方式（单边和双边对称分布）和障碍物纵横比（火焰传播方向的宽高比）对蒸汽爆燃的影响，在狭窄的阻塞通道中进行了一系列实验测试。使用了具有不同纵横比 0.9-2.1 的矩形障碍物。记录和分析火焰传播速度、火焰锋面结构、超压和障碍物附近的局部温度。结果表明，不同的障碍物分布模式不会从根本上改变爆燃火焰和超压的传播机制。障碍物边缘的剪切作用以及障碍物与通道边界之间的密闭空间结构形式都对爆燃火焰传播产生了显着影响。爆燃存在两个加速阶段，火焰速度峰值分别出现在障碍物上方和通道入口附近。具体而言，当纵横比为 1.8 时，最大火焰速度达到 102.5 m/s。此外，障碍物纵横比对火焰锋面有显着影响，火焰锋面结构在穿过障碍物时经历了复杂的变化。更重要的是，观察到一个有趣的反向火焰现象，导致更大面积的剧烈火焰燃烧。逆向火焰的最大长度随着障碍物纵横比的增大先减小后增大，这可能归因于流体的惯性力。因此，提出了一个简单的经验方程来预测火焰在狭窄的阻塞通道中传播过程中的反向火焰长度。该方程在当前应用范围内预测反向火焰长度方面表现良好。同时，局部温度峰值与受障碍物纵横比影响的局部爆燃反应强度密切相关。此外，还发现爆燃超压与火焰传播存在明显的耦合机制。爆燃超压和火焰速度几乎同时达到峰值。这种耦合机制可以显着扩大爆燃的影响范围。局部温度峰值与受障碍物纵横比影响的局部爆燃反应强度密切相关。此外，还发现爆燃超压与火焰传播存在明显的耦合机制。爆燃超压和火焰速度几乎同时达到峰值。这种耦合机制可以显着扩大爆燃的影响范围。局部温度峰值与受障碍物纵横比影响的局部爆燃反应强度密切相关。此外，还发现爆燃超压与火焰传播存在明显的耦合机制。爆燃超压和火焰速度几乎同时达到峰值。这种耦合机制可以显着扩大爆燃的影响范围。