Numerical study of diffusion filtration combustion characteristics in a plane-parallel packed bed

摘要

Numerical investigations on characteristics of diffusion filtration combustion are conducted in a plane-parallel packed bed. A detailed gas-phase reaction mechanism is used, and mass dispersion in packed bed is also taken into account. Attention is mainly focused on the combustion characteristics and the influencing factors, such as the gas and solid temperature profiles in the burner, the influences of solid thermal conductivity, mass dispersion and convective heat transfer between the gas and solid phases on the flame shape. The predicted results are compared with the available experimental and analytical data. For different gas mixture velocities and pellet diameters, the numerical model can successfully predict the flame shape. The predictions show that the diffusion combustion in packed bed remains the essential characteristics of normal diffusion combustion, although the solid properties can affect the flame structure. Compared with premixed combustion in porous media, there are two high temperature zones, which belong to gas and solid separately. These two high temperature zones locate at different positions in the burner. Results show that, the flame height remains almost the same with the increasing of thermal conductivity of solid but almost does not depend on the convective heat transfer between the solid and gas phases. In contrast, mass dispersion imposes significant influence on the flame structure. Higher mass dispersion will lead to the reduction of flame height but the increase of flame width. (C) 2015 Elsevier Ltd. All rights reserved.