Étude numérique de l'écoulement à froid et à chaud dans un brûleur poreux

Abstract

Combustion in porous media (CPM) has been pursued experimentally and numerically over the last decades and most numerical studies have been restricted to 1D and 2D simulations because of the encountered difficulties to reproduce a full 3D model due to sponge-like porous media normally used in CPM and computational cost. However, due to innovative 3D additive printing technology, it is now possible to print porous media with a user-specific design pattern. Based on this technology, this paper aims at modelling the flow behavior and combustion features of a homogeneous porous medium as would be printed using advanced additive technology. The numerical model is set up using the software STAR-CCM+ to solve the Navier-Stokes equations system for a compressible, laminar and unsteady flow. Nevertheless, the geometry of the porous medium remains relatively complex. Hence, the numerical model is built by first studying the flow past a cylinder as to determine the proper mesh size and distribution for an accurate flow representation at the microscale. Based on these results, the mesh is applied on the porous medium geometry reproduced in a representative volume. Analyses at macro and microscale of the cold flow through the porous medium are then carried out. Different flow rates representative of CPM and flow regimes are simulated as well as pressure drops along the medium are presented and showed a good agreement with the Darcy-Forchheimer pressure gradient law. Observations at the pore microscale are reported and depicted the fluid flow within the structure. Finally, the combustion of a reactive mixture is studied over a wide stable operation range. The main characteristics of the CPM are illustrated. At the microscale, the effects of the ordered structure are observed: the dispersion is reduced and the combustion is more homogeneous. The local temperature fluctuations are less important. This homogeneity leads to enhance the matrix lifetime and to reduce the pollutants emissions.

Date	25 Sept 2018
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Patrice Seers (Supervisor) & Louis Dufresne (Co-supervisor)