Comparative Study on the Combustion Performance in Localized Stratified and Rapidly Mixed Swirling Tubular Flame Burners

Experimental and computational results on the combustion performances and their formation mechanisms were presented and compared in two types of tubular flame burners by using methane as fuel. Results corroborate that the localized stratified tubular flame burner (LSSTFB) can achieve a large stability limit as a consequence of the edge-like flame structure, which is analogous to that of the edge flame. The edge-like flame structure in the LSSTFB is crucial for stabilizing the combustion and differs from that of the rapidly mixed burner. The global equivalence ratio can decrease to 0.18, which is considerably lower than that in the rapidly mixed burner. Additionally, the considerable stability limit can enable the occurrence of low temperature under ultra-lean conditions, whilst the edge-like flame structure can also reduce the NOx emission through the Fenimore mechanism. On the premise of the ensuring of the burn-off rate, the NOx emission in the LSSTFB is lower than that in the rapidly mixed burner.