Experimental and LES Investigation of a SGT-800 Burner in a Combustion Rig

The Siemens gas turbine SGT-800 has an annular combustor and 30 dry low emission burners. In order to further reduce the emission levels and to obtain improved understanding of the flow and associated flame dynamics, single burner rig tests have been performed. The laboratory measurements are complemented by Large Eddy Simulation (LES) to analyze the effect on the flame dynamics due to the transient fuel distribution and mixing process in the burner. The study includes both atmospheric and high pressure conditions. The computational model was developed jointly by Siemens Industrial Turbomachinery AB (SIT) and FOI. It is based on a finite rate chemistry LES model using a Partially Stirred Reactor (PaSR) turbulence chemistry interaction model and a two-step CH₄/air mechanism developed by FOI. The results are compared to measurements performed jointly by SIT and Lund Institute of Technology. The experimental data includes wall temperature, pressure fluctuations, light intensity variation and simultaneous Planar Laser Induced Fluorescence of OH and acetone. The study is further complemented by Reynolds Averaged Navier-Stokes (RANS) calculations of the fuel concentration field evaluated to laser measurements in a water rig using the same burner configuration. Different burner fuel distributions are examined and the corresponding influence on the downstream mixing, fuel distribution and flame dynamics are studied. The results indicate that the fuel distribution upstream the flame, the detailed modeling of the fuel supply manifold, including the specification of numerical boundary conditions, and the flow in the fuel and air supply pipes, have significant influence on the flame dynamics. This is proven by the successful combustion LES of an unstable flame that experiences high flame dynamics and that a modification of the boundary conditions alters the dynamics resulting in a more stable flame. This is well in accordance with the experimental data and previous experience at SIT. The modal structures caused by the interaction between the flow, acoustics and flame dynamics are analyzed using the Proper Orthogonal Decomposition (POD) technique. The dominating modes in general originate from the burner mixing tube air-fuel-mass flow-interaction and flame-combustion chamber interaction.