Stabilization mechanisms in localized stratified swirling tubular flame burner

The combustion characteristics of the localized stratified swirling tubular flame burner (LSSTFB) were investigated and compared with that in the rapidly mixed burner under lean conditions experimentally and numerically. In order to clarify the stabilization mechanisms of tubular flame in LSSTFB, the appearance of flame, species distribution, stability limit, heat release rate, and the flow field structure were investigated. Results show that the tubular flame stability limit of LSSTFB is much greater than that of the rapidly mixed burner. A specific distribution of species that the unburnt species distribute two sides of the reaction zone is formed in LSSTFB. It leads to the tubular flame with a binary structure processes both premixed and non-premixed flame characteristics. The internal recirculation in LSSTFB produces a lower local flow velocity and preheats the incomplete combustion gases, thereby increasing the balance between the flow field velocity and the flame propagation speed. Thus, in the localized stratified swirling tubular flame burner, there is a wider local equivalence ratio and flow velocity range suitable for flame stabilization.