LES-DFSD modelling of turbulent premixed flames past repeated obstacles

This paper presents simulations of propagating turbulent premixed deflagrating flames past built-in solid obstructions in a small-scale combustion chamber. The design of the chamber allows for up to three baffle plates and a central square obstacle to be positioned in the path of the propagating flames in order to generate turbulence and increase the flame propagating speed. The test case considered in this paper uses a stagnant, stoichiometric propane-air mixture in the configuration of three baffles and one central obstacle. Simulations have been carried out with the Large Eddy Simulation (LES) technique. The filtered reaction rate in LES is accounted for using a novel dynamic flame surface density (DFSD) model. Both numerical and experimental results show that the flame is initially laminar and becomes fully turbulent after continuous interaction with the obstacles downstream. Satisfactory agreement made between the LES calculations and the experimental data confirms the capability of the DFSD model in reproducing essential flame characteristic parameters including the maximum overpressure and flame front speed. The interaction between obstacle-generated turbulence and the flame front is quantified using the sub-grid-scale (SGS) wrinkling factor. Various stages of flame propagation and the dynamic behaviours of the flame are also examined based on the evolution and spatial distribution of the wrinkling factor.