Experimental work is reported for premixed flames propagating in tubes. The flames were ignited with a pilot flame and the flame propagation captured with high-speed cameras. Initial measurements were performed characterizing the rig. For downwardly propagating flames to a closed-end, methane and propane were studied. The flames initially propagated steadily, then at approximately a third of the way down the tube, the primary acoustic oscillation sets in, resulting to a change in the flame shape. This was then followed by a plateau of variable length before a more violent secondary acoustic oscillation. In some circumstances, flames were observed to rotate due to the primary acoustic instability. The flame front position growth rate for both methane and propane were similar despite the differences in the fuels. The total acoustic loss time for propane and methane increases from the lean limit with the equivalence ratio, peaks at =1.1 and then decreases as the mixture becomes richer. There was also an increase in the total acoustic loss time as the angular speed of the flame increased. The results showed that the generation of acoustic energy for propane was smaller than that of methane due to the stronger natural damping effect of the former.

中文翻译：

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向下传播的 CH4/C3H8 – 沿封闭管的空气火焰的比较研究

报告了在管中传播的预混火焰的实验工作。火焰被引燃火焰点燃，火焰传播由高速摄像机捕捉。进行了表征钻机的初始测量。对于向下传播到封闭端的火焰，研究了甲烷和丙烷。火焰最初稳定传播，然后在管子向下大约三分之一处，主要的声学振荡开始，导致火焰形状发生变化。然后是一段长度可变的平台，然后是更猛烈的二次声波振荡。在某些情况下，由于主要的声学不稳定性，观察到火焰旋转。尽管燃料不同，但甲烷和丙烷的火焰前沿位置增长率相似。丙烷和甲烷的总声学损失时间随着当量比从贫油极限增加，在 =1.1 处达到峰值，然后随着混合物变得更浓而减少。随着火焰角速度的增加，总的声学损失时间也增加了。结果表明，丙烷产生的声能小于甲烷，这是由于前者具有更强的自然阻尼效应。