Study of Combustor–Turbine Interactions by Performing Coupled and Decoupled Hybrid RANS-LES Simulations under Representative Engine-like Conditions

Combustion–turbine interaction phenomena are attracting ever-growing interest in recent years. As a matter of fact, the strong unsteady and three-dimensional flow field that characterizes the combustor is usually conserved up to the first-stage nozzle, possibly affecting its design and performance in terms of aerodynamics and the effectiveness of the cooling system as well. Such conditions are also exacerbated by the employment of lean-burn combustors, where high turbulence levels are required for the flame stabilization, resulting in even greater temperature and velocity distortions at the inlet of the first-stage nozzle. Even if it has been proven by several past studies that the best way of studying the combustor–turbine interaction is simulating the two components together, performing coupled simulations is still challenging from a numerical point of view, especially in an industrial context. For this reason, the application and generation of the most representative and reliable boundary conditions possible at the inlet of the S1N have assumed an increased importance in order to study the two components separately by performing decoupled simulations. In this context, the purpose of the present work is to compare fully integrated combustor–stator SBES simulations to isolated stator ones. To perform the stator-only calculations, the fully unsteady inlet conditions of the stator have been recorded at the interface plane between the two components in the integrated SBES simulation and then they have been reconstructed by applying the proper orthogonal decomposition (POD) technique. The SBES simulations of the isolated stator have been so performed with the aim of determining whether the flow field obtained is comparable with the one of the integrated simulation, thus allowing more realistic results to be obtained rather than imposing time-averaged 2D maps, as per standard design practice.