Flashback of an open turbulent, premixed flame in a swirl burner with central bluff-body is considered. The aim is to obtain further understanding of the physical mechanisms responsible for the upstream flame propagation. Previous studies on the same configuration hypothesised that there is an adverse pressure gradient in the direction of flame propagation. In this paper this is further investigated experimentally and theoretically. Static gauge pressure is measured on the surface of the bluff-body during flame flashback. Simultaneously, flame luminosity is imaged at 5 kHz. The results indicate that the static pressure rises downstream of the propagating reactive front. This is, then, discussed in the context of the theory of vortex bursting. An existing theory of flame propagation in the core flow is extended to a configuration similar to that investigated experimentally. The theory, although highly simplified, explains the generation of adverse pressure gradient across the flame and is qualitatively consistent with the experiment.
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