Influence of axial air injection on the flame stability of a technically premixed hydrogen flame

Abstract

This work is a numerical investigation on the stability of a hydrogen flame in a swirl-stabilized burner configuration using large-eddy simulation with tabulated chemistry. Experimental results from this combustor showed that the axial injection influences the vortex breakdown (VB) position and therefore, the propensity of the burner to produce flashback. It is found that depending on the combination of primary swirl flow and amount of axial air injection, the flow can exhibit self-excited oscillations, and more importantly, it can control the flashback safety. Numerical simulations are used here to investigate different combinations of axial air injection and evaluate its impact on flame stability and flashback resistance. It is found that the axial air injection influences the flame stabilization and the position of the central recirculation zone. The penetration of the flame in the mixing tube introduces a strong expansion and acceleration of the flow, which results in a reduction of the spreading angle and eventually a flashback event.