Investigations Of Premixed Combustion In Inert Porous Media

The study of the combustion in porous media has become an international hotspot because combustion in porous media has the virtues of the high combustion efficiency and the low emissions. The premixed combustion in porous media was studied experimentally and numerically in this paper. The numerical simulation, the main task of the paper, includes three parts: one-dimensional laminar premixed combustion modeling, one-dimensional turbulent combustion modeling and two-dimensional combustion modeling.The numerical simulation of the combustion in porous media using one-dimension steady laminar reacting model was intensively studied with the interphase convective heat change and dispersion effects, the detailed mechanism and two-flux radiative transfer equation. The numerical method was also carefully studied to solve the steady premixed flame propagation with eigenvalue. The stability and convergence are strengthened by optimizing the initial value, the iterative method and the numerical gird.The influence of different chemistry reaction mechanisms and dispersion effects was numerically analyzed firstly. The results show that one-step mechanism has the same result with the detailed mechanism with small equivalence ratio, and the detailed mechanism should be included with large equivalence ratio. Four detailed mechanisms, GRI 3.0, GRI 2.11, GRI 1.2 and Peters, were studied. The results show that GRI 3.0 mechanism is the best, and Peters mechanism is the worst. The influence of the dispersion effects is large with relatively large equivalence ratio, and the computational result can be greatly improved if the dispersion effects are considered.The flame structure, the flame propagation and stability, the emissions and the radiative output efficiency in a one-layer and a two-layer porous porous burner were also studied. The combustion in a porous burner has more special characteristics such as superadiabatic flames, broader lean flammabilities, higher flame propagation speed, et al. compared to the combustion in a free space burner. The flame is easily stabilized between the two layers in a two-layer porous burner to overcome the shortcomings of the flashback and blow up in a one-layer porous burner. The turbulent model should be taken into account since the laminar method was not suitable for higher gas velocity in burner. The one-dimensional turbulent model was developed and numerically studied in porous burner. The flame propagation speed and the emissions of NO and CO with the turbulent model are better than that with laminar method. It should be noted that a more accurate model is needed to have better predicted NO emission.The two-dimensional combustion simulation in porous burner was performed to take into account the effects of the viscosity and the heat loss from the wall, which was also used to validate the assumptions in the one-dimensional model. The flow and flame is approximately one-dimensional in porous media due to the very thin boundary layer in 2-D simulation.The C₃H₈/Air premixed flames in the AL₂O₃ porous ceramic foam were observed and measured. The conclusions by computation are well agreed to that by experiment.