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This paper presents pore scale simulation of turbulent combustion of air/methane mixture in porous media to investigate the effects of multidimensionality and turbulence on the flame within pore scale. A porous medium consisting of a staggered arrangement of square cylinders considered here. Results of turbulent kinetic energy, temperature, flame thickness, flame structure and flame speed are presented and compared at different equivalence ratios. The turbulent kinetic energy increases along the burner because of turbulence created by the solid matrix with a sudden jump at the flame front due to increase of the velocity as a result of thermal expansion. Also, it is shown that at higher equivalence ratios, the effect of turbulence within porous burner is highly significant phenomenon. Due to higher turbulence effects in higher equivalence ratios, the flame thickness increases by increasing the equivalence ratio which is in opposite of the trend observed in laminar flow simulation. Also, it is shown that the dimensionless flame speed and excess temperature is higher at lower equivalence ratios due to lower heat loss to the cold upstream environment of burner. Two dimensional structure of flame in the pores of porous medium is shown in the present study via isotherm lines.

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According to the significant effect of the structure and saturation of cathode catalyst layer (CCL) on the operation of proton exchange membrane fuel cell (PEMFC), a pore scale model is presented to simulate the transport processes in CCL. Using this model, the tortuosity and macroscopic effective diffusivity of CCL with different porosities and saturation levels were obtained. The water distribution was obtained by solving two-phase flow equations using volume of fluid (VOF) method. The structure of CCL was reconstructed by assuming agglomerates as equally-sized circles and spheres in two-and three-dimensional domains, respectively. A sequential algorithm was used to determine the location of agglomerates in the computational domain with specific overlap. A comparison was made between the results obtained for three- and two-dimensional domains which showed 2D assumption results in an overestimating on effective diffusivity. However, the variation trend of effective diffusivity versus porosity was about the same. According to the results, due to the blocking effect of water presence in CCL, the increase of saturation causes less available pathways for gas to diffuse. Therefore, the effective diffusivity decreases by the increase of saturation level. Moreover, the decrease of porosity leads to the increase of tortuosity which results in lower pathways for gas to diffuse into the domain and hence less effective diffusivity was obtained. The decrease of oxygen effective diffusivity of CCL causes a lack of oxygen concentration at the electrochemical reaction sites and leads to the decrease of the PEMFC performance.