Effects of air dilution in a lean premixed swirl burner with mixture stratification

Numerical simulations using LES with tabulated chemistry based on the Flamelet Generated Manifold (FGM) method are conducted with the aim to understand the influence of mixture stratification on the flame dynamics on a swirled burner with bluff body. This configuration consists of a main injection of premixed fuel (CH4) with air in rich conditions, injected into a coflow of swirled air which will further mix along a premixing length prior to the combustor, resulting into a global mixture burning in lean conditions. While maintaining the global equivalence ratio inside the combustion chamber to ϕg = 0.8, three operating conditions are simulated, which differ on the mass fraction of air premixed with methane (5, 10 and 15 %). Different flame topologies are obtained, and a qualitative comparison with experiments is performed.