Computational modelling of micro-structured burners with improved combustion stability by fluid recirculation structures
While burners designed in a backflow way enable operation with very low noxious emissions, they frequently operate very close to the extinction limit of the flame. Cavity structures have been designed for the purpose of improving flame stability. However, the precise mechanism by which the cavity method provides increased flame stability remains unclear. Computational fluid dynamics simulations are conducted to gain insights into burner performance such as reaction rates, species concentrations, temperatures, and flames. Factors affecting combustion characteristics and flame stability are determined. The results indicate that burner dimensions greatly affect flame stability. Burners with large dimensions lead to a delay in flame ignition and may cause blowout. The combustion is stabilized by recirculation of hot combustion products induced by the cavity structure. The inlet velocity of the mixture is a critical factor in assuring flame stability within the cavity-stabilized burner. There is a narrow range of inlet velocities that permit sustained combustion within the cavity-stabilized burner. Design recommendations are provided.
Keywords: Burners; Flames; Temperatures; Species concentrations; Reaction rates; Combustion