Numerical Study of Unsteady Flow-Field and Flame Dynamics in a Gas Turbine Model Combustor

Abstract

In swirl-stabilized gas turbine combustors, interaction between unsteady flow-field and flame dynamics play a key role in driving several types of combustion instabilities, establishing flame location and its structure and influencing heat release rates. This is challenging to understand and computationally expensive to resolve in detail. In this study, a highly turbulent and swirling flow-flame dynamics in a gas turbine model combustor is characterized numerically using unsteady Reynolds-averaged Navier Stokes (URANS) and detached eddy simulation (DES) based computational fluid dynamics (CFD) methods. From flame representation point of view, the Flamelet Generated Manifold (FGM) method is used to reduce combustion chemistry (which still includes detailed reaction kinetics and species diffusion in reaction layers) and hence computational requirements. The helical precessing vortex core (PVC) instability and its influence on downstream flow/flame dynamics is captured. Further insight is gained into URANS and DES methods capabilities in simulating various coherent swirl flow structures such as central toroidal recirculation zone (CTRZ) and outer recirculation zones (ORZ) as well as fuel-air mixing patterns. NOx emission, which is currently a high-priority design objective due to stringent pollutant regulations, is also computed. The results show that the numerically captured swirling flow-flame dynamics is in accordance with the experimental observations and measurements.