Experimental and numerical studies on combustion characteristics of N2-diluted CH4 and O2 diffusion combustion in a packed bed

Experimental and numerical studies were conducted to determine the combustion characteristics of gas diffusion combustion in a porous combustor packed with 2.5 mm or 3.5 mm alumina pellets，special attention is focused on the effect of packed bed height (h) on combustion, NO and CO emissions. The pollutant emission of diffusion filtration combustion is studied with different packed bed lengthsin the range of 40 mm≤h≤240 mm, fixed excess air ratio of 1.88 and fixed gas inlet velocity of 0.06 m/s. Results show that both immerged and surface flames coexist in the combustor. Although porous media enhances the mixing and diffusion processes, the diffusion flame shape is still observed from the side and top views of the combustor, the diffusion filtration remains properties of diffusion combustion. The immersed flame is always observed with increase in h, whereas the height of surface flame decreases. The NO emission decreases sharply when his increased from 40 mm to 120 mm. However, the NO em...