Modeling and Simulation of Pollutant Formation in Gas Turbines

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For the development of gas turbine engines, pollutant formation during combustion plays a significant role. Due to increasingly stringent emission limits, further improvements and optimization with respect to emissions is required. Numerical simulations can contribute to cost reduction and acceleration of this development process. However, regarding pollutant emissions, a lack in the predictive quality of state-of-the-art combustion models often limits the usefulness of numerical results. The goal of the proposed research project is therefore the development, validation, and application of simulation models, which can provide reliable predictions of pollutant emissions in gas turbine combustors. In order to reach this goal, an integrated modeling approach is proposed, which combines Large-Eddy Simulations (LES) with the use of combustion and emission models that are based on detailed chemistry. In coordination with the project partners of the FVV, the project has been subdivided into two work packages in order to address the different aspects of pollutant emissions in the development of gas turbine combustors. In aero engines, soot emissions constitute a great challenge, while in stationary gas turbines, the increase of CO emissions at part load poses limitations for the development of load-flexible systems. During the first two years of the project, an emission model for CO was developed for laminar combustion. It accounts for the change in the timescales of the CO production and consumption processes under part load conditions and decouples these processes from the remaining part of the combustion model. For soot emissions, the focus was on the statistical treatment of the soot Number Density Function. Using a novel quadrature-based moment method, especially soot oxidation could be described more accurately. In the second phase of the project, the focus will be on the interaction of turbulence and pollutant formation. To this end, Direct Numerical Simulations (DNS) will be performed for different configurations, which represent the combustion processes and pollutant formation in stationary gas turbines as well as in aero engines. The resulting data will be systematically analyzed using the Optimal Estimator method. Based on the findings obtained regarding the pollutant/turbulence interactions, both pollutant models will be formulated for turbulent combustion in the context of LES. Toward the end of the project, all model components from both the previous and the next project phases will be integrated into an existing Multi-Regime combustion model. This integrated model will be applied to a model combustor as well as a real aero engine.