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Combustion LES Software for Improved Emissions Predictions of High Performance Gas Turbine Combustors

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Final rept.

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Low emissions of CO, NOx, and unburned hydrocarbons UHC are a difficult challenge in the design of new military gas turbine combustors. Simulation tools that can predict emissions are needed to reduce the cost of producing improved, low emissions combustor designs. In this SBIR, CFD Research Corporation CFDRC continued to develop combustion Large Eddy Simulation LES techniques to create a high fidelity tool for predicting emissions. The LES code was improved by the development and implementation of a new multi-step assumed PDF method that accounts for more detailed kinetics with turbulent chemistry interactions. This new method enables efficient turbulent combustion CFD calculations for both steady state Reynolds Averaged Navier Stokes RANS and LES with multi-step global mechanisms. Tabulation methods were implemented and tested for improved computational efficiency. Improvements to the existing combustion models and inlet boundary conditions for LES were also performed. In addition to the new turbulent combustion models, the capability to generate the necessary global mechanisms from detailed reaction mechanisms was developed. The final code was validated against benchmark experimental data, and applied to the Rolls-Royce JSF combustor. Validation cases included both premixed and diffusion flames covering a broad range of flame conditions. Although much progress was made in this Phase II effort, continued work is needed to make the new multi-step assumed PDF model robust and practical. In particular, a new solver for the species transport equations needs to be implemented to reduce run times by a factor of two or more.

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  • Jet and Gas Turbine Engines

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