||In this study, established a two dimensional CFD model with orthogonal mesh to simulate the combustion phenomenon of methane-air mixture gas in the radiation combustor. The combustion chamber of this model which consists of a cellular array was simplified to modeling flame propagation inside a channel, and therefore parameters effects of flame ignited location and efficiency of this combustor has been discussed. Using ANSYS FLUENT and user-defined function (UDF) to simulate flame propagating and heat radiation, and using DO model of ANSYS FLUENT to simulate surfaces emissivity. In this study, considering methane and air stoichiometric combustion modeled by a simple one-step irreversible reaction|
The results reveal that increase of thermal conductivity results in the increase of adiabatic flame propagating speed and temperature, and thus flame propagats to upstream side. However, when thermal conductivity greater than 20 W/m-K, it was limited for the effects of thermal conductivity to increasing adiabatic flame temperature. If the inlet fuel velocity increase, it needs longer distance to achieve 100% fuel consumption. Flame propagating to the downstream side heats the methane-air mixture gas closed to the downstream side, increases downstream radiation heat flux , reduces radiation heat loss flux to the environment of upstream side and results in worse combustion efficiency. With certain equivalence ratio, at the limit fuel inlet velocity, it causes the maximum adiabatic temperature, but with large solid thermal conductivity it can employ wide range of fuel inlet velocity. With case of large equivalence ratio, adiabatic flame speed and temperature, it needs a shorter distance to achieve 100% fuel consumption, also leads to flame propagate to the upstream side and increases the radiation heat loss. Downstream radiation heat efficiency would increase with increasing perforated-plate internal emissivity. Overall, using a combustor which consists of lower equivalence ratio, lower fuel inlet velocity, lower perforated-plate conductivity, and higher perforated-plate internal emissivity,will gain better radiation heat efficiency.