Innovative Subgrid-Scale Combustion Modeling for Gas Turbines

New high-efficiency, low-emission, fuel-flexible gas turbine designs will operate at fuel lean conditions near the flame blow-out limit. To maintain high efficiency and flame stability under these conditions, a detailed knowledge of the flame dynamics will be required from both experimental and computational studies. From a computational perspective, accurate turbulent combustion models are required to evaluate advanced turbine designs. However, current combustion models applied for design analysis lack the necessary physical modeling to accurately predict flows near the lean blow-out limit. Under this proposed effort a new and innovative modeling strategy will be developed to accurately predict flows near the lean blow-out limit. This new model will also be computationally inexpensive so that it may be applied routinely within design analysis. The objective of this program is to develop a fast running, turbulent combustion model for large eddy simulation (LES) that will be accurate for all flame regimes of gas turbine operation, including near the lean blow-out limit. This new formulation will be based on a parameterization of the linear-eddy model (LEM). The LEM is a comprehensive mixing model that accurately captures the interaction of flow turbulence with flame structure in all flame regimes. Statistics from this model will be parameterized in terms of a reduced set of variables and stored within a database that is used to produce the required closure statistics for an LES prediction. This model will be fast because the closure statistics are retrieved from a database and not computed during the simulation. The model will also be general and applicable to all flame regimes because the closure statistics will be produced from the LEM formulation. Commercial Application and Other Benefits: A software tool kit developed under this effort will produce the model statistics and database required for an LES prediction. The database for a particular problem may be used within any CFD flow solver, and for RANS flow solvers as well. Combustion models generated by the tool kit will be applicable to a wide range of military and commercial combustion applications including gas turbines, power generation systems, furnaces, incinerators, internal combustion engines, aircraft engines, etc. CRAFT Tech will market this tool kit for license to commercial customers as well as to other CFD flow solver development companies.