Numerical simulation of cavity flow structure in an axisymmetric trapped vortex combustor

Abstract

Reacting and non-reacting flow structure in a three dimensional (3D) trapped vortex combustor (TVC) cavity was investigated numerically by using shear stress transport (SST) k–ω model and eddy dissipation combustion model. In order to validate the present numerical model, the predicted results were compared with the experimental results available in literature for the same conditions. The pressure drop for various cavity aspect ratios, and the flow field predicted by the numerical model matched reasonably well with the experimental data. Non-reacting flow studies revealed that the secondary air jet momentum does not have significant effect on cavity flow structure, however, fuel–air mixing was observed to be improved for the higher momentum flux ratio (MFR) case. In contrast, under reacting flow conditions, the cavity flow structure was highly sensitive to secondary air jet momentum. For higher MFR cases, the cavity flow was characterized by multiple vortices, which were caused due to the volume expansion associated with combustion. Hence, it could be concluded that, under reacting flow conditions, cavity flow structure is highly dependent on the momentum flux ratio between the cavity and the mainstream flow. Besides this, the influence of turbulence associated with flow accompanied with the generation of baroclinic torque might also be a cause for the vortex breakdown, which has to be investigated extensively.