Premixed combustion of hydrogen/methane mixtures in a porous medium burner

The premixed combustion of hydrogen-methane mixtures in porous medium burners is investigated numerically. The numerical model considers solid and gas phase energy equations separately, and includes nongray radiation transport for the solid phase. GRI-Mech 2.11 is used for the detailed chemical kinetic model. The lean limit of pure methane can be extended from φ= 0.53 for free flame to φ= 0.4 for porous medium flame. Adding hydrogen in the fuel, the lean limit can be further reduced to φ = 0.35. The flame speeds of porous ceramic burner flames are several times as that of free flames. For φ= 1.0, the free flame speed of methane is about 40 cm/s whereas that of porous burner flame is 87 cm/s approximately. Adding hydrogen to the fuel, the flame speed is increased to 103 cm/s when the fraction of hydrogen in the fuel, g, equals to 0.3. Increasing g to 0.6 raises the flame speed to 142 cm/s. The CO and NO _x emissions increase slightly as the hydrogen fraction in the fuel is raised.