An experimental and theoretical study of porous radiant burner performance

We have studied experimentally the stability and heat transfer characteristics of lean premixed, methane-air flames embedded in a porous layer. The work is directly relevant to understanding the performance and operating behavior of porous radiant burners (PRB). Flame speed and radiant output data were obtained for different stoichiometries and flame locations in porous ceramic foam. The results indicate that stable combustion at elevated flame speeds can be maintained in two different spatial domains: one spanning the upstream half of the porous region and the other in a narrow region near the exit plane. The heat release and radiant output are also found to increase as the flame is shifted toward the middle of the porous layer. A one-dimensional laminar premixed flame model incorporating a radiatively participating inert porous medium was used to describe the test conditions. Calculations using a one-step reaction confirmed the observation of two stable flame regions. The predicted flame speeds and radiant output agree favorably with the experimental trends.