Effects of the preheat layer thickness on surface/submerged flame during porous media combustion of micro burner

The applications of porous media burners are of massive interest to researchers from decades, and still trending in the modern world because of their tremendous advantages, such as high thermal efficiency and low emissions. In this work, a microburner was made to achieve surface and submerged flame region for different thicknesses of preheat layers. A reaction layer of alumina foam with a predefined thickness was used, whereas the preheat layer of porcelain foam was replaced with three different thicknesses namely 5, 10, and 15 mm. By using 5 mm preheat layer, only surface flame was visible with absolutely no trace of submerged flame region, while 10 and 15 mm can undergo both surface and submerged flame region. Equivalence ratio of 0.7 was observed to give best performance with regards to surface flame, while 0.5 for submerged flame region. Only 10 mm can able to give highest thermal efficiencies reaching 90% and 38% for the surface and submerged flame region respectively. Finally, low emission rate for NOx and CO was seen for all the possible individual cases.