Numerical study of the premixed propane/air flame characteristics in a partially filled micro porous combustor

Highlights: • Porous medium improves the flame temperature due to heat recirculation. • Porous medium reduces the heat loss from the outer wall. • Higher wall thermal conductivity improves the heat recirculation. • The lower limits mainly depend on the heat loss from flame root to porous medium. • Higher wall thermal conductivity boosts the chemical reaction inside porous medium. -- Abstract: In order to enhance the heat recirculation in micro combustors, a micro planar combustor partially filled with porous medium was developed. The objective of the present work is to study the interaction between the heat recirculation and the flame stability. The thermal non-equilibrium model was employed to investigate the heat transfer between the gas and porous medium. The results show that adding porous medium in micro combustor causes higher flame temperature and reduces the heat loss effectively. The stable operation range under different equivalence ratios was identified. The heat convection between gas and porous medium dominates the heat recirculation process. The gas-to-porous convection efficiency decreases with the increase of inlet velocity and equivalence ratio, while the gas-to-wall convection efficiency decreases first and then increases with the increase of inlet velocity. Higher wall thermal conductivity can increase the upper inlet velocity limits significantly, but it has negligible effect on the lower limits. The lower limits mainly depend on the heat loss from flame root to porous medium. The low temperature chemical reaction R179 "i-C3H7+O2=C3H6+HO2" occurs in porous medium for wall thermal conductivity of 150 W/m-K. The results above can provide guideline for the design of a high-efficiency micro porous combustor.