Investigation of flame structure and precessing vortex core instability of a gas turbine model combustor with different swirler configurations

Abstract

Numerical simulation of a dual-swirl gas turbine model combustor is performed under cold and reacting flow conditions using a three-dimensional unsteady Reynolds-averaged Navier–Stokes approach. A multi-species chemical mechanism is used in this study for the analysis of the numerous radicals participating in the ignition process and the flame structure. The other objective of this study is to investigate the flow field under different injector configurations, including both co-rotating and counter-rotating swirler arrangements, different swirl intensities, and vane areas. A comparison of the results with experimental data shows that the predicted velocity and temperature profiles follow the experimental data reasonably. In these studies, a precessing vortex core is found in the shear layer of the inner recirculation zone for all injector arrangements considered, and a co-rotating vortex exists in the outer shear layer for some of these arrangements. OH mass fraction field shows that the reactions take place mostly near the vortex core. Furthermore, it is shown that the build-up process of H2O2 and CH2O inside the cold jet has an important effect on combustion initiation. In addition, the formation and consumption of the H atoms in the recirculation zones and the balance between OH and H2O2 are shown to have important roles in the flame formation process. Finally, the precession frequency of the PVC is found to scale almost linearly with the spatial gradient of swirl velocity in the inner swirler and almost independent from the inclusion of the combustion reactions.