Numerical study of flame inclination instability in a packed bed with extra lean methane/air intake by an adaptive multi-scale model

The common numerical method to simulate the evolution of flame instability during filtration combustion mainly includes volume average method and pore scale simulation. However, they are not satisfying in computation accuracy and cost respectively. In this paper, a self-developed adaptive multi-scale model is built to study the inclination instability of the flame front in a packed bed with honeycomb ceramics. The perturbations on the distribution of the intake parameters and physical properties of fillings in the packed bed lead to the flame inclination. The influences of the amplitude and range of the perturbations on the flame inclination development are investigated. The development mechanism of flame inclination is analyzed by method of flow competition (MFC) theory. The results show that the increase of the flame inclination angle will enhance the transversal heat transfer. Subsequently, the radiation and conduction fluxes restrain the increase of the flame inclination. Under the same level of perturbation amplitude, the result shows that the influence sequences of the four factors for the flame inclination are as follows: fillings porosity, feed flow rate, fillings heat capacity, and feed concentration. In addition, larger amplitude of perturbation leads to higher maximum flame inclination angle. However, the perturbation range has little influence on the development of flame inclination angle. Finally, the flame inclination is restrained successfully through adding new perturbation of intake parameters or elimination of initial perturbation. The above. studies are quite meaningful to the stable operation and wide application of porous media combustion technology in the utilization of low calorific value gas energy.