Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.
Large Eddy Simulations of gaseous flames in gas turbine combustion chambers
