Heat release imaging in turbulent premixed methane-air flames close to blow-off
Heat release imaging in turbulent premixed methane-air flames close to blow-off
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DOI：
10.1016/j.proci.2014.05.144
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. Kariuki;A. Dowlut;R. Yuan;R. Balachandran;E. Mastorakos
中科院分区：
文献类型：
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作者：
J. Kariuki;A. Dowlut;R. Yuan;R. Balachandran;E. Mastorakos
在越来越接近吹离的条件下，测量了稳定在轴对称海崖体上的无约束稀薄预混甲烷-空气火焰的热释放（HR）估计值。同时进行OH-和CH 2 O-PLIF成像，并使用OH-和CH 2 O-PLIF图像的逐像素乘法获得HR测量值。通过缓慢降低燃料流速来接近吹脱。在远离吹离的条件下，HR沿剪切层沿着发生，而在接近吹离的条件下，在回流区（RZ）内也观察到HR。在远离吹离的条件下，沿着火焰前缘观察到局部的沿着收缩，并且随着吹离的接近，频率和尺寸增加。在接近吹离的条件下，在RZ内的火焰袋的边界上检测到HR，该火焰袋在附着点处与碎片火焰分离。在吹离附近的RZ中没有OH的区域经常被CH 2 O填充。也观察到OH和CH 2 O的空白区域，但不太常见，表明在RZ内存在预热气体和新鲜反应物。这些图像没有显示与环形空气射流的连接，这意味着冷反应物从顶部进入RZ。HR被观察到增加作为一个函数的火焰前曲率的绝对值为近单位刘易斯数火焰调查。这里报道的测量是有用的模型验证和探索的湍流预混火焰结构的变化，作为灭绝的做法。
Estimates of the heat release (HR) of unconfined lean premixed methane–air flames stabilized on an axisymmetric bluff body have been measured for conditions increasingly closer to blow-off. Simultaneous imaging of OH- and CH2O-PLIF was performed, and HR measurements obtained using the pixel-by-pixel multiplication of the OH- and CH2O-PLIF images. Blow-off was approached by slowly reducing the fuel flow rate. At conditions far from blow-off, HR occurred along the shear layer, whereas at conditions near blow-off, HR was also observed inside the recirculation zone (RZ). Localised extinctions along the flame front were seen at conditions away from blow-off, and increased in frequency and size as blow-off was approached. At conditions near blow-off, HR was detected on the boundary of flame pockets inside the RZ which had detached from the fragmented flame at the attachment point. Regions void of OH in the RZ near blow-off were often seen to be filled with CH2O. Regions void of both OH and CH2O were also observed, but less often, indicating the presence of both preheated gases and fresh reactants inside the RZ. Such images do not show a connection with the annular air jet, implying the cold reactants entered the RZ from the top. HR was observed to increase as a function of the absolute value of flame front curvature for the near unity Lewis number flames investigated. The measurements reported here are useful for model validation and for exploring the changes in turbulent premixed flame structure as extinction is approached.