Application of Large Eddy Simulation for HA_Class Combustion System Design to Mitigate Combustion Instabilities (Frequency, and Amplitude)

Enabled by national commercialization of massive shale resources, Gas Turbines continue to be the backbone of power generation in the US. With the ever-increasing demand on efficiency, GT combustion sections have evolved to include shorter combustion lengths and multiple axial staging of the fuel, while at the same time operating at ever increasing temperatures. This paper presents the results of very detailed Large Eddy Simulations of one (or two) combustor can(s) for a 7HA GE Gas Turbine Engine over a range of operating parameters. The model of the simulated combustor can(s) includes (include) all the details of the combustor from compressor diffuser to the end of the stationary part of the first stage of the turbine. It includes the geometries of multiple pre-mixers within the combustion can(s) and the complete design features for axial fuel staging. All simulations in this work are performed using the CharLES flow solver developed by Cascade Technologies. CharLES is a suite of massively parallel CFD tools designed specifically for multiphysics LES in high-fidelity engineering applications. Thermo acoustic results from LES were validated first in the physical GE lab and then in full-engine testing. Both the trend as well as the predicted amplitudes for the excited axial dominant combustion mode matched the data produced in the lab and in the engine. The simulations also revealed insight into the ingestion of hot gases by different hardware pieces that may occur when machine operates under medium to high combustion dynamics amplitudes. This insight then informed the subsequent design changes which were made to the existing hardware to mitigate the problems encountered.