Flame acceleration due to flame-induced instabilities in large-scale explosions
Flame acceleration due to flame-induced instabilities in large-scale explosions
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DOI：
10.1016/s0010-2180(00)00208-x
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发表时间：
2001-03-01
影响因子：
4.4
通讯作者：
Puttock, JS
中科院分区：
文献类型：
--
作者：
Bradley, D;Cresswell, TM;Puttock, JS
本文报道了大气压下初始静止的甲烷-空气和丙烷-空气混合物的大规模爆炸，在爆炸中测量了半球形火焰的火焰速度，其半径刚好超过3米。蜂窝状火焰发展得相当快，此后火焰速度随时间的平方根不断增加。使火焰起皱的不稳定波长的范围随着火焰传播而增加，这增加了火焰速度。可以看出两种火焰传播状态。首先，存在一个初始稳定区域，在该区域中，火焰通过热扩散和火焰拉伸而稳定，并且燃烧速度与Markstein长度和火焰拉伸率有关。其次是第二个制度，在该制度中，在达到临界佩克莱数后，火焰不再稳定，不稳定性增长，使火焰起皱，并增加火焰速度。火焰速度的理论表达式为这两个政权。第二个依赖于火焰不稳定性理论，随着火焰传播，不稳定波长的范围越来越大。火焰半径随时间的理论预测在这两个制度是在很好的协议与实验观察。随着火焰的发展，细胞尺寸被测量。这些都是相当接近的理论波长，在不稳定的火焰振幅的增长率是最大的。(C)2001年，燃烧研究所。
Large-scale explosions of initially quiescent methane-ah and propane-air mixtures at atmospheric pressure are reported, in which the flame speed of a hemispherical flame is measured up to radii just beyond 3 m. A cellular flame is developed fairly soon and thereafter the flame speed increases continually with the square root of the time. The range of unstable wavelengths that wrinkle the flame increases as the flame propagates and this increases the flame speed. Two flame propagation regimes can be discerned. First, there is an initial stable regime, in which the flame is stabilized by thermo-diffusion and flame stretch, and the burning velocity is related to the Markstein length and rats of flame stretch. This is followed by a second regime in which, after a critical Peclet number has been attained, the flame is no longer stable, instabilities grow, wrinkle the flame, and increase the flame speed. Theoretical expressions for flame speed are presented for both regimes. That for the second rests on flame instability theory, with an increasing range of unstable wavelengths as the flame propagates. The theoretical predictions of flame radius with time over both regimes are in good agreement with those observed experimentally. Cell sizes are measured photographically as the flame progresses. These are fairly close to the theoretical wavelengths at which the rate of growth of the unstable flame amplitudes are a maximum. (C) 2001 by The Combustion Institute.