Flame propagation in swirling flows -: Effect of local extinction on the combustion induced vortex breakdown

The interaction of chemical reaction and swirling flows can lead to accelerated flame propagation. In this context, the combustion induced vortex breakdown (CIVB) has been identified in previous studies as prevailing flashback mechanism in swirl burners. However, quenching of the chemical reaction can prevent the upstream flame propagation due to a CIVB. The present study shows that this limiting criterion can be described by a quenching constant that is balancing the chemical time scale with a time scale for the flow. The most appropriate chemical time scales are based on perfectly stirred reactor (PSR) simulations. To consider the influence of the preferential diffusion typical for hydrogen, the PSR time scales are corrected by the Lewis number. Once the quenching constant is determined experimentally for a specific burner configuration, the flashback limits for various operating conditions and fuels can be predicted. Finally, the pressure scaling of the flashback limits is discussed.