---

This paper investigates suitable approximation for Calculating the thermal radiation flux divergence and effect of errors on performance evaluation of porous radiant burners (PRB).Thus, a single layer and a double layer of buried flame type of the porous radiant burners have been selected and numerically simulated. Due to the significant difference in the temperature of the solid matrix and the fluid passing the burner, the energy equations was considered as a non-local thermal equilibrium. Complete kinetics of methane air was used for combustion modeling. Since the effect of lateral walls should be neglected the problem was solved in 1D to present exact solution of RTE and compares the other approximations. Results show that discrete ordinate as well finite volume approximation of RTE show that eight directional spherical split is the best selection. Lower ordinates have substantial deviation and increasing the number of division enlarges computation cost without any considerable improvement on errors reductions. Furthermore, two flux method and Rosseland approximation are not valid for this kind of modeling.

---

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.

---

In the present study, the effect of intra-pore turbulence within porous burnershas been investigated on combustion of methane/air mixture in such burners. A model is adapted to the porous structure to models turbulence flow. The GRI 3.0 chemical reaction mechanism is utilized for the combustion of methane/air mixture and radiative part of the solid phase energy equation is obtained using the discrete ordinate method. The numerical results show that the gas temperature obtained from turbulence model stays below the corresponding laminar model temperature all over the combustion region, and the flame thickness becomes wider in turbulence model. Although the CO emission are insensitive to laminar or turbulence model, the burning speed and NO emission predictions are found to be significantly improved when the effects of turbulence are taken into account.

---

In this paper, experimental comparison between conventional burner and porous burner in domestic purposes as stove, according to Iranian National Standard No. 10325 has been carried out. This comparison between the conventional burner available in the Iranian market and its equivalent porous burner is done. First, flammability of the porous silicon carbide burner was investigated. The results showed that the flame is formed when the equivalence ratio is less than 1, so the best performance equivalence ratio was around 0.7. By changing the distance between the pot and the burner and also changing the pot diameter, it was found that for a pot with 26 cm diameter and burner distance of 1 cm, porous burner efficiency increases to 55%. The comparison between the conventional burner and optimum situation porous burner showed that at the same factors like power, distance between the pot and the burner, the pot diameter, the burner diameter, measuring tools and the same method, porous burner efficiency is 1.5 times more than conventional burner. In conventional burners CO and NOX pollutant are 8-26 and 8 times more than porous burners. Due to higher efficiency and lower emissions, conventional burners can supersede porous burners for domestic purposes.