Compressible Large Eddy Simulation of Thermoacoustic Instabilities in the PRECCINSTA Combustor using Flamelet Generated Manifolds with Dynamic Thickened Flame Model

The fully compressible, density-based CFD-solver TRACE has been extended for simulations of turbulent reacting flows in aero engine gas turbine combustors. The flamelet generated manifolds combustion model is utilized to account for detailed chemical kinetics and combined with the dynamically thickened flame model to resolve the flame front on the large eddy simulation (LES) mesh. The chemistry tabulation is coupled with the LES solver by inversion of the transported energy equation using tabulated mixture averaged NASA polynomial coefficients. LES of the PRECCINSTA test case, a lean, partially-premixed swirl combustor are performed and the two distinctive regimes are correctly predicted: a stable regime with a 'quite' stable flame and an unstable regime with an oscillating flame driven by self-excited thermoacoustic instabilities. Statistics collected from the simulations, mean and root-mean-square values, are in good agreement with the experimental reference data for both operating conditions. The dominant frequency of the unstable flame deviates from the measurement by about 100 Hz and requires further investigation. The results demonstrate the general suitability of the simulation framework for reacting flow simulations in gas turbine combustion systems and the prediction of self-excited thermoacoustic oscillations