We experimentally studied the flame behavior of H–O–N premixed gas around a T-shaped bifurcation in a piping system with an inner diameter of 20 mm. In the experiments, we measured the flame speed as a function of the path length from the igniting spark plug using ion probes and observed self-emission images using a high-speed camera. The speed and disturbance of the flame entering the bifurcation were varied by installing various numbers of obstacle rods into the pipe just downstream of the igniting spark plug. We compared the effects of the bifurcation on the flame propagation between two cases: the flame propagating straight through the T-shaped bifurcation and the flame turning 90° at the T-shaped bifurcation. In both cases, the flame was accelerated around the T-shaped bifurcation. Especially, in the case of the flame turning 90° at the T-shaped bifurcation, the flame acceleration was remarkable and, in some cases, a detonation was initiated immediately downstream of the T-shaped bifurcation. The observed remarkable flame acceleration is considered to be ascribed to the recirculation region formed by the separation of the unburned-gas flow downstream of the T-shaped bifurcation, and governed by the ratio between the ignition delay time of the mixture of the burned and unburned gases and the sound-crossing time for the pipe diameter which is the only length scale of a long pipe.

中文翻译：

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T 形分叉周围的火焰加速和爆炸引发

我们通过实验研究了内径为 20 mm 的管道系统中 T 形分叉周围 H-O-N 预混合气体的火焰行为。在实验中，我们使用离子探针测量了火焰速度与点火火花塞的路径长度的函数关系，并使用高速相机观察了自发射图像。通过在点火火花塞下游的管道中安装不同数量的障碍棒，可以改变进入分叉处的火焰的速度和扰动。我们比较了两种情况下分叉对火焰传播的影响：火焰直接穿过T形分叉传播和火焰在T形分叉处转向90°。在这两种情况下，火焰在 T 形分叉处加速。特别是，在T形分叉处火焰旋转90°的情况下，火焰加速显着，并且在一些情况下，在T形分叉处紧下游引发爆炸。观察到的显着火焰加速被认为归因于 T 形分叉下游未燃烧气流分离形成的再循环区域，并由已燃烧和未燃烧混合物的点火延迟时间之比控制。气体和声音穿过管径的时间，管径是长管的唯一长度尺度。