This paper studies the flame dynamics near lean blowout (LBO) conditions in a stratified swirl burner. The novel BASIS burner is used and fueled with premixed methane/air mixture at atmospheric conditions. In the experiments, only the pilot flame works with four different equivalent ratios. It is found that as the flame changes from stable combustion to near LBO, the flame macrostructure changes from V-shape to M-shape. Meanwhile, a characteristic frequency of 405 Hz is found in the spectrum of heat release signal. The closer to LBO, the higher amplitude is found at the frequency peak. Post-processing of flame images illustrates that the 405 Hz comes from the circumferential movement of the flame. Large-eddy simulations (LESs) via OpenFOAM reproduce the flame dynamics near LBO, which agrees with the experimental results. LESs provide more insights into the flow fields, showing that the characteristic frequency of 405 Hz comes from the flame-vortex interaction. This study reveals the mechanism of flame and vortex interactions in a stratified swirl burner near LBO. The heat release signal is also found can be used as a candidate precursor for LBO.

本文研究了分层旋流燃烧器中接近贫燃 (LBO) 条件的火焰动力学。使用新型 BASIS 燃烧器，并在大气条件下以预混合的甲烷/空气混合物为燃料。在实验中，只有引燃火焰以四种不同的当量比工作。发现随着火焰从稳定燃烧转变为接近LBO，火焰宏观结构由V形转变为M形。同时，在放热信号频谱中发现了405Hz的特征频率。越接近 LBO，在频率峰值处发现的幅度越高。火焰图像的后处理表明 405 Hz 来自火焰的圆周运动。通过 OpenFOAM 的大涡模拟 (LES) 再现了 LBO 附近的火焰动力学，这与实验结果一致。LES 提供了对流场的更多见解，表明 405 Hz 的特征频率来自火焰 - 涡流相互作用。这项研究揭示了 LBO 附近分层涡流燃烧器中火焰和涡流相互作用的机制。还发现热释放信号可用作 LBO 的候选前体。