Response of a laminar premixed flame to flow oscillations: A kinematic model and thermoacoustic instability results
Response of a laminar premixed flame to flow oscillations: A kinematic model and thermoacoustic instability results
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DOI：
10.1016/0010-2180(96)00049-1
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发表时间：
1996-09
影响因子：
4.4
通讯作者：
M. Fleifil;A. Annaswamy;Z. Ghoneim;A. Ghoniem
中科院分区：
文献类型：
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作者：
M. Fleifil;A. Annaswamy;Z. Ghoneim;A. Ghoniem
燃烧不稳定性是由于系统声学与非定常热释放之间的耦合而产生的共振现象。这两个过程之间的建设性反馈取决于许多参数，其中包括声模态、火焰支架特性和主导燃烧模式，这种反馈通常发生在压力与非定常放热率之间满足一定的相位关系时。本文建立了一个分析模型，描述了稳定在管边缘的层流预混火焰对速度振荡的动态响应。我们考虑均匀和非均匀速度扰动叠加在管道流速剖面上。模型结果表明，热释放扰动的大小及其相对于动态扰动的相位主要取决于火焰的斯特劳哈尔数，它代表了主导频率乘以管半径与层流燃烧速度的比值。根据这个数字，高频扰动通过火焰，而低频则导致强烈的响应。相对于速度摄动的相位则相反。该模型的计算结果与实验结果一致，可用于确定如何在各种声不稳定模态中选择燃烧激发模态。然后利用该模型得到了描述整个频率范围内速度扰动与放热响应关系的时域微分方程。
Combustion instability is a resonance phenomenon that arises due to the coupling between the system acoustics and the unsteady heat release. The constructive feedback between the two processes, which is known to occur as a certain phase relationship between the pressure and the unsteady heat release rate is satisfied, depends on many parameters among which is the acoustic mode, the flame holder characteristics, and the dominant burning pattern. In this paper, we construct an analytical model to describe the dynamic response of a laminar premixed flame stabilized on the rim of a tube to velocity oscillation. We consider uniform and nonuniform velocity perturbations superimposed on a pipe flow velocity profile. The model results show that the magnitude of heat release perturbation and its phase with respect to the dynamic perturbation depend primarily on the flame Strouhal number, representing the ratio of the dominant frequency times the tube radius to the laminar burning velocity. In terms of this number, high-frequency perturbations pass through the flame while low frequencies lead to a strong response. The phase with respect to the velocity perturbation behaves in the opposite way. Results of this model are shown to agree with experimental observations and to be useful in determining how the combustion excited mode is selected among all the acoustic unstable modes. The model is then used to obtain a time-domain differential equation describing the relationship between the velocity perturbation and the heat release response over the entire frequency range.