In this experimental research, a porous wall is used to stabilize a premixed flame. The effect of the porous wall on the flame length, CO, and NO x emissions for natural gas and air combustion is studied at a fixed power burner. A cylindrical flame holder with 154 mm length, 90 mm inner diameter, and 160 mm outer diameter is used as a combustion chamber. The SiC porous walls have outer diameter of 90 mm, inner diameter of 40, 50, and 60 mm, pore density of 10, and 30 PPI, and length of 22, 44, and 66 mm. A Testo 350 XL gas analyzer is used to measure emission pollutants. It is observed that the flame length increases with an increase in the pore density and the length of porous wall and a decrease in the inner diameter of porous wall. An appropriate correlation is proposed to estimate the flame length at constant pore density and power burner. Also, the results revealed that NO x concentration increases with increasing inner diameter and length of porous wall and decreases with increasing pore density of porous wall. CO results show that CO concentration only depends on the equivalence ratio and the physical characteristics of the porous wall does not affect it. Keywords Premixed burner • Porous wall • Flame length • NO x • CO List of symbols A Area (m 2) d Inner diameter (mm) H Length (mm) LHV Lower heat value (kj/m 3) PPI Pore per inch P Burner power (kW) m Mass flow rate (kg/s) T Temperature (°C) W Uncertainty of the dependent variable w Uncertainty of the independent variable Greek symbols ρ Density (kg/m 3) ϕ Equivalence ratio

In the present analysis, the flame stabilization and temperature distribution within a premixed burner contain porous wall are studied experimentally. The effects of inner diameter, length, and pore density of the porous wall, thermal load, equivalence ratio, and the inlet velocity of the fuel-air mixture on these are studied.The fuel used in this study is natural gas and the porous wall is SiC (silicon carbide) ceramic foam. The experimental results clearly indicate that the axial temperature along the porous wall increases when the inner diameter of the porous wall decreases and its length increases. The porous wall temperature with an inner diameter of 40 mm, length of 66 mm, and pore density of 30 PPI (pores per inch) has the highest temperature among the examined states. The results of studying the effect of the porous wall on flame stability show that the flame stability limit has a direct relationship with the length and pore density of porous wall and an inverse relationship with the inner diameter of the porous wall. Also, it is found that the porous wall has the highest temperature causes the maximum flame stability limit.