预混旋流火焰热声不稳定性的成像诊断研究

Imaging Diagnosis of Thermo-acoustic Instability in Premixed Swirl Combustion

以丙烷-空气旋流预混火焰为实验对象,针对几种特定工况,通过可见光、近红外光、OH基化学自发光三种波段分别研究了自激振荡与外激振荡下的火焰特征,通过动态模态分解法(DMD)对火焰与热气体的动力学特性进行了分析;结果发现不稳定燃烧时旋流火焰与热气体的发光强度峰值存在一个时间延迟,DMD得到的火焰不稳定频率与热气体不稳定频率接近,并与麦克风采集到的声学脉动频率吻合,燃烧不稳定处于纵向模态,外激振荡与自激震荡下的火焰与热气体有着相似的动力学行为。本文采取的可见光和近红外自发光成像观测方法为研究热声不稳定提供了一种新的成像方法,对以后研究燃气透平进口热斑迁移机理提供了一种新的思路.

For propane-air premixed swirling flames,swirling flames under self-excited oscillation and external excited oscillation are studied by imaging of visible light,near-infrared light,and OH^* chemiluminescence under several specific conditions.The dynamic characteristics of swirling flames and hot burnt gas are analyzed by dynamic mode decomposition(DMD)method.The results show that there is a time delay between the peak intensity of the swirling flame and the hot burnt gas during unstable combustion.The instability frequency of the flame and the hot burnt gas obtained by DMD is the same,which is close to the acoustic pulsation frequency captured by the microphone signal.The combustion instability is in the longitudinal mode.The external excitation and the self-sustained oscillation leave similar effect on both flame and hot burnt gas.The visible light,near-infrared light imaging observation method adopted in this paper provides a new imaging method for the investigation of thermoacoustic instability,and provides a new idea for the future study of the hot spot migration mechanism in gas turbine.