Burning velocity of triple flames with gentle concentration gradient
Burning velocity of triple flames with gentle concentration gradient
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DOI：
10.1016/j.proci.2006.08.068
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
M. Hirota;T. Yokomori;K. Yasuda;Y. Nagai;M. Mizomoto;G. Masuya
中科院分区：
文献类型：
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作者：
M. Hirota;T. Yokomori;K. Yasuda;Y. Nagai;M. Mizomoto;G. Masuya
研究了二维甲烷-空气三重火焰在矩形燃烧器中的局部火焰速度。分别用粒子图像测速仪和瑞利散射法测量了速度场和浓度分布。为了使火焰前缘的局部浓度梯度保持一致，存在一个必要的初始速度和初始浓度梯度组合。在这些情况下，火焰的曲率也是一致的。因此，燃烧速度由火焰曲率决定，定义为三相点处的局部流动速度。当火焰曲率接近于零时，燃烧速度随火焰曲率的增大而增大。在此之后，燃烧速度随曲率的增大而减小。峰值超过了绝热一维层流燃烧速度。比较测量的火焰拉伸速率对流动应变κ沙子火焰曲率κc的影响，κ比κ较大且增加得更快，当火焰曲率满足1/rf<；250m−1时，κ变得恒定，而−仍增加250m/lt；1/rf时，κc值比κS大得多，燃烧速度的峰值大致在上述火焰曲率的转折处。因此，低浓度梯度下的燃烧速度与火焰拉伸速率相关。
We investigated the local flame speed of a two-dimensional, methane–air triple flame in a rectangular burner. The velocity fields and the concentration profiles were measured with particle image velocimetry and the Rayleigh scattering method, respectively. There was a requisite combination of initial velocity and initial concentration gradient for consistency of the local concentration gradient at the leading edge of the flame. In these cases, the flame curvatures were also consistent. Accordingly, the burning velocity, defined as local flow velocity at the triple point, was determined by the flame curvature. The burning velocity increased with increasing flame curvature, when the curvature was near zero. After that, the burning velocity decreased with increasing curvature. The peak value thus exceeded the adiabatic one-dimensional laminar burning velocity. Comparing the effects of the measured flame stretch rate on the flow strain κsand flame curvature κc, κsis larger and increases more rapidly than κcfor flame curvatures satisfying 1/Rf<250m−1and then becomes constant while κcstill increases for 250 m−1<1/Rf, so that κcbecomes much larger than κs. There is also a peak in burning velocity at roughly the transition in flame curvature specified above. Therefore, the burning velocity for a low concentration gradient correlates with the flame stretch rate.