中文摘要：

利用实验和数值模拟方法对贫燃预混旋流火焰的动力学失稳过程进行了分析，发现燃烧室入口非反应旋流入射过程所诱发的低频压力振荡将引起反应流热声振荡，两者之间具有倍频关系；旋流剪切边界层内较高的速度梯度诱导产生小尺度漩涡，三维螺旋结构的涡漩进动过程将造成火焰面内出现周期性的局部熄火和重新着火，从而使非平衡羟基等值面和中心回流区尺度出现周期性变化，并进一步诱发低频、高幅压力振荡，导致火焰发生动力学失稳；涡漩进动、中心回流区尺度、非平衡羟基等值面变化及压力振荡具有相同的频率．

英文摘要：

Experimental and numerical analysis of unstable lean premixed swirl methane/air flames was conducted using vibration analyzer and large eddy simulation （LES） models for reactive turbulent flows. Thermoacoustic oscillations were caused by low frequency pressure oscillations induced by nonreactive swirl flow. The frequencies of thermoacoustic oscillations were a multiple of the characteristic frequency of pressure oscillations. The processing vortex core （PVC） was believed to be caused mainly by the high velocity gradient in inner shear layer of swirl flow, which created three-dimensional helical contorted structure in swirl flame. Periodical PVC could cause regional quenching and reignition, resulting in the inner recirculation zone （IRZ） periodical ＂heartbeat＂ phenomena, further causing low frequency pressure oscillation in the combustion chamber and unstable flames. PVC occurrences, OH isosurface pulsation, heartbeat of IRZ and pressure oscillation all have the same frequency.