Numerical study of flame/vortex interactions in 2-D trapped vortex combustor

Abstract

The interactions between flame and vortex in a 2-D trapped vortex combustor are investigated by simulating the Reynolds averaged Navier-Stokes equations, for the following five cases: (1) non-reacting (base) case, (2) post-vortex ignition without premixing, (3) post-vortex ignition with premixing, (4) pre-vortex ignition without premixing, and (5) pre-vortex ignition with premixing. For the post-vortex ignition without premixing case, the reactants are mixed well in the cavity resulting in a stable C shaped flame along the vortex edge. Further, there is insignificant change in the vorticity due to chemical reactions. In contrast, for the pre-vortex ignition case (no premixing); the flame gets stabilized at the interface of two counter rotating vortices resulting in reduced reaction rates. There is a noticeable change in the location and size of the primary vortex as compared to case (2). When the mainstream air is premixed with fuel, there is a further reduction in the reaction rates and thus structure of cavity flame gets altered significantly for case (5). Pilot flame established for cases (2) and (3) are well shielded from main flow and hence the flame structure and reaction rates do not change appreciably. Hence, it is expected that cases (2) and (3) can perform well over a wide range of operating conditions.