Pore-scale study of complex flame stabilization phenomena in thin-layered radial porous burner

摘要

During the last years the thin-layered radial porous burners are of growing interest, primarily due tolow pressure loss, advanced flame stability and high radiant output. The aim of this study is to investigatethe flame stabilization phenomena in radial flow burner using a pore-scale approach with directsimulation of the realistic three-dimensional porous structure and interstitial flow with thermal interactionbetween the fluid and solid phases including surface radiation. The stabilization mechanisms areinvestigated with focus on the detailed inner flame structure and its aerodynamical and thermal interactionwith the porous shell. The results demonstrate that three characteristic combustion regimes can bedistinguished, namely, the internal, submerged and surface-stabilized flames that form depending on themixture composition and the flow rate. The general principles governing change of regimes are discussed.A key factor of the internal flame stabilization within the burner cavity is a kinematic balance betweenflow and burning velocity. When the reaction zone submerges the porous shell, the heat recuperationbecomes an important factor of flame stabilization. In the surface-stabilized regime, the large velocitygradients lead to the highly stretched and curved flames that aerodynamically anchor at the external surfaceof the shell analogously with the perforated plates and bluff bodies but have wrinkled shape due tothe nonuniformity of the flow field within irregular porous structure. A characteristic diagram of regimechange is proposed. It is discussed that for porous burners with size of structural elements of the samemagnitude as shell thickness, application of the quasi-homogeneous assumption is restricted in contrastto the pore-scale simulation approach that considers as a prospective technique for studying combustionphenomena.