Combustion characteristics of porous media burners under various back pressures: An experimental study

The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various back pressures, investigating flame stability and figuring out the distribution laws of combustion gas flow and resistance loss, so as to achieve an optimized design and efficient operation of the devices, a bench of foamed ceramics porous media combustion devices was thus set up to test the cold-state resistance and hot-state combustion characteristic of burners in working conditions without back pressures and with two different back pressures. The following results are achieved from this experimental study. (1) The strong thermal reflux of porous media can preheat the premixed air effectively, so the flame can be kept stable easily, the combustion equivalent ratio of porous media burners is lower than that of traditional burners, and its pollutant content of flue gas is much lower than the national standard value. (2) The friction coefficient of foamed ceramics decreases with the increase of air flow rate, and its decreasing rate slows down gradually. (3) When the flow rate of air is low, viscosity is the dominant flow resistance, and the friction coefficient is in an inverse relation with the flow rate. (4) As the flow rate of air increases, inertia is the dominant flow resistance, and the friction coefficient is mainly influenced by the roughness and cracks of foamed ceramics. (5) After the introduction of secondary air, the minimum equivalent ratio of porous media burners gets much lower and its range of equivalent ratio is much larger than that of traditional burners.