Large Eddy Simulations of Acoustic Combustion Phenomena Inherent to Gas Turbine Engines

ABSTRACT: Development, implementation and validation of a computational model to simulate combustion processes coupled with acoustic phenomena is critical to quantitatively predict acoustic waves inherent to gas turbine engines, i.e. screech and rumble. For a rigorous high-fidelity numerical model for acoustic combustion in engine augmentors, we identified several critical technology components. These include compressible LES, low Mach number schemes, efficient time advancement, non-reflecting boundary conditions, turbulent combustion modeling for LES, Lagrangian multiphase modeling for liquid breakup and evaporation, and a CFD method that accurately, yet efficiently captures high frequency acoustic waves in a complex geometry setting. Most of these required technology components are already available in the IllinoisRocstar Rocstar Simulation Suite physics modules. We propose a series of enhancements for the purpose of adding new physics, bringing the existing models closer to first principles, and increasing the numerical efficiency and accuracy. We include a validation roadmap that will systematically validate the high-fidelity methodology, starting from academic canonical problems to realistic augmentor geometries and physics of engineering interest. These include premixed combustion, liquid fuel injection, breakup and evaporation, some non-premixed spray combustion, all coupled with resolved acoustic waves and turbulent fluctuations, and their corresponding subgrid scale effects. BENEFIT: The IllinoisRocstar Chimera-overset mesh code, RocfloCM, and multiphase particle software tool, Rocpart, will be fully embedded within a commercially-oriented design tool for predictive modeling. The Phase II anticipated result is that we will have fully demonstratedon realistic hardware geometries and flow conditionsa new methodology that permits high-fidelity predictive simulations of the effects of acoustic combustion instabilities on engine augmentor performance and integrity. This demonstration will substantially extend the state of the art in terms of computational efficiency and predictive accuracy, when compared against current commercial and in-house tools. We expect that this new methodology will be an enabling technology for the high-fidelity prediction of turbulent combustion flows in complex gas turbine augmentor applications. This program will provide pathways to two salable products: software and engineering services. Software: A validated tool to predict acoustic combustion instabilities in engine combustors will be available from this work. It will be of commercial quality, and have great modeling flexibility due to its modular, multiphysics module structure, and incorporate state-of-the-art methods for modeling augmentor rumble and screech instabilities. All DoD mission agencies have interest in predicting propulsion instabilities due to acoustic combustion (e.g. Army, MDA, Navy, Air Force and NASA), and many U.S. industry and government agencies can also benefit from the capabilities of a flexible, validated modeling package. Government prime contractors providing engine technologies to the government will be licensing targets for the package. Engineering services: Analytical and consulting services will be available based on the validated capabilities at the end of Phase II. These services are needed by the DoD components, aircraft manufacturers and their tier-two and -three suppliers. The Phase III application of this technology will initially address the mission service project offices for prime contractors in the market.