Experimental investigation on propagation characteristics of n-heptane/air combustion wave in foamed porous media

Although porous media combustion is suitable for micro/meso-scale power systems, the accurate flame dynamics in porous media have not been revealed, which are critical for understanding the flame stabilization mechanism. In this work, the propagation characteristics of combustion wave in the porous media are investigated. In the experiments, a clear blue flame front is observed and the instantaneous flame speed is determined. The flames in porous media both exhibit characteristics of pulsating propagation at different heating powers and pore densities. The average speed of the laminar submerged flame is much lower than that of the free flame, ranging from 0.20 mm/s to 0.97 mm/s, which is mainly caused by the wall quenching effect. The preheating temperature has a significant effect on flame propagation. Furthermore, as the pore density increases from 10 ppi to 30 ppi, the maximum speed of the flame decreases, while the average speed increases and then decreases. The average flame speed is comprehensively influenced by wall quenching and heat recirculation effects.