CFD simulation of premixed flames propagating in an obstacles network

The objective of this work is to study the propagation of a premixed flame through numerous obstacles and to observe the flame/obstacle interactions. Several premixed flame models have been evaluated using the OpenFoam software library. They are all based on the evolution of the progress variable and they take into account the increase of the flame speed due to the effects of folding and stretching due to the turbulence. The studied configuration is based on the expansion of a spherical flame within a network of obstacles whose spherical geometry allows fine statistical analyses along the radial direction of the geometry. Various analyses have been carried out based on the temporal evolution of the flame, on the geometric position of its front and finally on the statistical data of its structure. At a given level of turbulence and for an equal volume obstruction rate, whatever the arrangement of the obstacles, it appears that the flame surface developed over time remains substantially identical even if its local topology is very different. On the other hand, if the volume of obstructions varies, the flame surface and therefore its propagation speed is strongly affected. Different correlations for turbulent combustion models have been used: Gulder, FLACS and Zimont. These are the most used in the most common industrial CFD codes. It has been observed that, by properly adjusting the parameters associated with each model, an identical free flame velocity can be found by each model, however, as soon as the flame crosses obstacles, significant variations are observed. This is a logical observation since these models were developed for flame propagation without obstacles. But it seems necessary to consider extensions of these models that would take into account the presence of a given volume obstruction rate.

Automated summary

The objective of this study is to investigate the propagation of a premixed flame through obstacles and the interactions between flame and obstacles. Different premixed flame models were evaluated using OpenFoam, all of which are based on progress variable evolution and consider the increase in flame speed due to turbulence effects.