EXPERIMENTAL AND NUMERICAL STUDY OF PREMIXED COMBUSTION WITHIN NONHOMOGENEOUS POROUS CERAMICS

An experimental and numerical investigation of premixed methane combustion within a nonhomogeneous porous ceramic was performed. The burner consisted of two porous ceramic cylinders of equal length and diameter that were stacked together and insulated around the circumference. Four series of experiments were carried out to determine the lean limit using three different pore sizes in the downstream ceramic cylinder (SBR). The pore size in the upstream ceramic cylinder was constant in all four cases. A new definition of the lean limit was introduced to account for the effects of the porous ceramic. The burners were tested over the range of lean limit 0.41 < PSI less-than-or-equal-to 0.68 and the numerical simulations were performed over 0.43 < PSI less-than-or-equal-to 1.0. The results demonstrated that porous ceramic burners provide a range of stable burning rates at a constant PSI. The maximum flame speed inside the burners was much higher than the premixed, freely burning adiabatic laminar flame (free flame) speed. The lean limits in the porous burners were lower than that of the free flame. The effects of SBR pore size on the burner performance were also determined. Flame stability characteristics at the interface and exit plane are revealed both numerically and experimentally. The numerical model in this study predicts the combustion phenomena within the porous ceramics with reasonable accuracy. The model can be used to guide future experimental burner designs and tests.