Experimental Investigation on Effect of Height and Pore Density of Porous Medium on Flame and Emission Characteristics of Inverse Diffusion Combustor

Abstract

The flame structure, appearance, and emission characteristics of an inverse diffusion porous combustor (IDPC) are investigated experimentally. Unstructured ceramic foam made of silicon carbide (SIC) is used as a porous medium. At stoichiometry conditions, a reactive analysis is performed with methane as a fuel and variations in the pore distribution density (pore density) of ceramic foam SIC. Height of ceramic foam and Reynolds number of air jet (\({{\operatorname{Re} }_{{air}}}\)) are varied. Porous medium alters flow momentum in radial and axial directions which affects flame appearance and emissions. Increased radial momentum produces wider and shorter flame in case of IDPC. A bright blue zone is detected at the base of the flame, and a luminous orange or orange-blue zone is observed in the post-combustion zone near the flame tip. As the pore density is enhanced from 10 pores per inch (PPI) to 20 PPI, the flame is detached from the surface of the porous medium at a higher Reynolds number of the air jet. The visible flame height of IDPC is significantly reduced at 10 PPI when compared to a case without a porous medium. The Reynolds number of the air jet and the pore density of the porous medium strongly influence the emission levels of NO_x and CO. The IDPC with porous media height of 28 mm, \({{\operatorname{Re} }_{{air}}}\) = 8122 and 10 PPI pore density performs optimum in terms of flame shapes and CO and NO_x emissions.