Experimental Study on the Coupled Response Characteristics of Multiple Flames in an Afterburner Cavity/Bluff-Body Configuration

<jats:p>This study experimentally investigates the influence of fuel nozzle configuration on the dynamic response and stability mechanisms of coupled flames in a bluff-body/cavity model afterburner under atmospheric conditions. The research focuses on the interrelations among the flame transfer function (FTF), modal energy distribution, and transient flame structures. The results demonstrate that a distinct band-pass gain peak emerges near 100 Hz for the single spray hole configuration, whereas this peak is absent for the triple spray holes configuration. Further analysis reveals that the dynamic response characteristics of the flame depend critically on the spatial coherence of the heat release process. In the bluff-body/cavity configuration, the single spray hole flame exhibits a concentrated heat release zone with strong spatial coherence, leading to a pronounced band-pass FTF gain peak at a specific frequency (100 Hz). In contrast, for the triple spray holes flame, the heat release process is spatially dispersed and phase coherence is disrupted. This attenuation of the overall coherent response results in the absence of a significant gain peak across the external excitation frequency range of 0-200 Hz.</jats:p>