Simulation of reacting flows in packed beds using flamelet generated manifolds

The propagation speed is a key characteristic of a premixed flame since it determines its location and shape. Its correct prediction is particularly important when the flame propagates in a packed bed due to the acceleration of the inflow mixture as it passes through the interstices and the potential interaction with the walls surrounding the interstices. Since the kinetic mechanism has an effect on the propagation speed, the use of detailed chemical kinetics is desired. To limit the cost of chemistry resolution, the feasibility of using the flamelet generated manifolds method (FGM) is investigated. A 2D laminar premixed methane/air flame with a co-flow of air, which propagates into a packed bed, is set up as a test case. The packed bed is either represented by a porous medium or by a resolved approach where particle shapes are fully resolved. The solutions using chemistry tables and finite rate chemistry with a detailed mechanism (GRI3.0) under adiabatic conditions and with heat exchange between the two phases are in good agreement. In addition, the computational effort using FGM is about 13 times lower. In a next step, the employed FGM approach is validated against experiments. For this purpose, an experimentally investigated 2D premixed flame confined by three isothermal cylinders is simulated using flamelet generated manifolds for three operating conditions. Comparison of simulated and measured flame shape and location shows reasonable agreement. This proves that the flamelet generated manifolds method is suitable and cost-effective to simulate reacting flows within packed beds.