High-fidelity prediction of metal temperature in gas turbine combustors using a loosely coupled multiphysics approach

Aeroengine industry is being largely affected by the mid- and long-term targets of civil aviation, that is searching for increasingly efficient low-emission engines and new opportunities as in the segment of small aircraft. The dynamically evolving market requires prompt solutions for the combustor that cannot be easily provided by experiments because of technical issues and expensive campaigns. On the other hand, the progressive developments in the field of massively parallel computing is making Computational Fluid Dynamics the most effective tool for a deep insight of combustion chambers. Indeed, high-fidelity investigations on this component is a multiphysics problem requiring to model the interactions between turbulence, combustion, radiation and heat transfer. Thermal design is a key task in the development loop of novel combustors, being stressed by lower coolant availability and higher power density. For this purpose, CFD-based models are required to properly account for the 3-D heat load distribution. Nevertheless, the limits of standard RANS approaches in accurately modelling highly-turbulent reacting flow is well-known and nowadays scale-resolving methods, as Large-Eddy Simulation (LES), Detached Eddy Simulation (DES) and Scale Adaptive Simulation (SAS), are the most promising ones; the latter, in particular, is emerged as a valid trade-off for industrial applications. In the present work a multiphysics tool, called U-THERM3D, is proposed as potential approach for the prediction of metal temperature in the context of scale-resolving simulations. The tool is validated on predictable solutions and applied to two burners, the DLR model aero-engine combustor and the LEMCOTEC combustor. The former is a laboratory sooting flame simulated using LES and the focus is on the tool capabilities in modelling the involved interacting phenomena. The latter is an effusion cooled lean-burn aeroengine combustor investigated from different perspectives using SAS to predict exit profile temperature, emissions and metal temperature. To the author's knowledge no works can be found in literature on multiphysics simulations of lean burn combustors relying on Scale Adaptive Simulation. For this reason the present work aims to be a reference for high-fidelity final design as well as a starting point for future activities. The results in both the burners are compared against steady THERM3D simulations and experiments emphasizing the detrimental effects of the swirling flow on the wall temperature, that acts increasing the heat transfer coefficient and reducing the film cooling coverage. The improved prediction of metal temperature obtained by U-THERM3D shows the potential of this tool as a framework for the high-fidelity design of gas turbine combustors. Obviously, the accuracy of the coupled simulation can benefit from the improvement in the different involved models and further research efforts should be focused on this task.