Computational modelling and simulation of forward-smouldering of porous media in a fixed bed

In order to evaluate the performance and optimal operating conditions of forward smouldering in a cylindrical porous medium, a numerical code has been developed that permits prediction of the smouldering propagation (slow-burning) of foam insulation materials in bi-dimensional configuration. The finite volume discretisation and the bi-conjugate gradient stabilised method are used to solve the system of governing equations. The chemical kinetics model is based on a first order pyrolysis reaction, followed by oxidation of the porous fuel and the carbonaceous residual. This second reaction of oxidation might promote the transition from smouldering to flaming, and thus, fire initiation. The gas and solid temperature, the oxygen and the char mass fraction temporal evolutions are computed, based on the adopted chemical kinetics model, and the assumed heat and mass transfer coefficients. The smoulder propagation velocity is then determined. The developed code featured a CPU time, of the simulated phenomena, of the order of 47 hours on a typical Pentium 4 configuration, which represents a significant improvement compared to many previously applied algorithms. The developed code is able to simulate any smouldering and/or reacting front propagation through a fixed bed.