Direct Numerical Simulation of Flame/Acoustic Interactions

Abstract

Combustion phenomena are of high scientific and technological interest, in particular for energy generation and transportation systems. Direct Numerical Simulations (DNS) have become an essential and well-established research tool to investigate the structure of turbulent flames, since they do not rely on any approximate turbulence models. In this project the DNS code π ³C is employed to investigate different flame configurations. This DNS code is an explicit, three-dimensional code solving the fully compressible, reactive Navier-Stokes equations. Chemistry is described through tabulation, using two coordinates to enter a database constructed for example with 29 species and 141 reactions for methane combustion. The tabulation procedure has been first validated using a laminar household burner configuration computed with the in-house laminar combustion code $\mbox{\textit{\textsf{UGC}}}^{+}$ . DNS is used here to investigate the growth of a turbulent premixed flame in a methane-air mixture. For this purpose a perfectly spherical laminar flame kernel is initialized at the center of a cubic domain at zero velocity. A field of synthetic, homogeneous isotropic turbulence is then superposed and the turbulent flow and the flame can begin to interact. Various species can be used as an indicator for the flame front in a combustion process. Among them, the isosurface of carbon dioxide (CO₂) at a mass fraction of 0.03 is retained here, since this value corresponds to the steepest temperature gradient in the associated, one-dimensional laminar premixed flame. The obtained results have been post-processed in order to study some interesting aspects of the coupling between flame kernel evolution and turbulence, such as straining and curvature, flame surface area and local thickness.