Characterization of flame macrostructures and inter-dome interactions in a centrally staged model combustor

This paper presents an experimental investigation on flame interactions and macrostructures between adjacent domes in a centrally staged triple-dome model combustor under different main-stage equivalence ratio (∅m) and stratification ratio (SR) conditions. This work employs direct photograph and high-speed flame chemiluminescence of CH* and OH* measurements. The degree of interaction is quantitatively evaluated by examining the relative CH* intensity of a few key locations and comparing the intensity on the wall side with that on the adjacent dome side. Flame CH* imaging also reveals three distinct flame macrostructures (single-layer, double-layer, and triple-layer) and two inter-dome flame interaction modes [inverted V-shape (IVS) and inverted funnel-shape (IFS)]. Results demonstrate that flame macrostructures are predominantly influenced by SR variations, while interaction modes were determined solely by ∅m conditions. Compared to the IFS mode, the IVS mode shows an interaction region located closer upstream. Moreover, two distinct interaction-induced phenomena are identified: a stable outer flame in the main-stage jet outer shear layer, and an intermittent pocket flame within the inter-dome triangular recirculation zone. Analysis of local equivalence ratios and high-speed OH* image sequences shows that outer flame stabilization depends primarily on heat feedback from the sub-interaction backflow region, while the intermittent behavior of pocket flame is attributed to the periodic flame fragment detachment in the interaction region.