气体透平模型燃烧器中部分预混和旋流火焰瞬态现象的平面时间分辨测量
This paper presents observations and analysis of the time-dependent behaviour of a 10 kWpartially pre-mixed, swirl stabilized methane-air flame exhibiting self-excited thermo-acousticoscillations. This analysis is based on a series of measurements wherein particle imagevelocimetry (PIV) and planar laser-induced fluorescence (PLIF) of the OH radical wereperformed simultaneously at 5 kHz repetition rate over durations of 0.8s. Chemiluminescenceimaging of the OH* radical was performed separately, also at 5 kHz over 0.8s acquisitionruns. These measurements were of sufficient sampling frequency and duration to extractusable spatial and temporal frequency information on the medium to large-scale flow-fieldand heat-release characteristics of the flame. This analysis is used to more fully characterizethe interaction between the self-excited thermo-acoustic oscillations and the dominant flowfieldstructure of this flame, a precessing vortex core (PVC) present in the inner recirculationzone. Interpretation of individual measurement sequences yielded insight into variousphysical phenomena and the underlying mechanisms driving flame dynamics. It is observedfor this flame that location of the reaction zone tracks large-scale fluctuations in axial velocityand also conforms to the passage of large-scale vortical structures through the flow-field.Local extinction of the reaction zone in regions of persistently high principal compressivestrain is observed. Such extinctions, however, are seen to be self healing and thus do notinduce blow-out. Indications of auto-ignition in regions of unburned gas near the exit are alsoobserved. Probable auto-ignition events are frequently observed coincident with the centers oflarge-scale vortical structures, suggesting the phenomenon is linked to the enhanced mixingand longer residence times associated with fluid at the core of the PVC as it moves throughthe flame.