Numerical Study of NOx and Flame Shape of a DLE Burner

For natural gas combustion, there is a large amount of experience in the gas turbine industry. However, much of the design work is based on costly combustion tests due to insufficient accuracy of existing prediction tools for data such as emissions and effects due to fuel composition. In the present work, Computational Fluid Dynamics (CFD) approach is used to study partially premixed combustion in the 3rd generation DLE (Dry Low Emission) burner that is used in SGT-700 and SGT-800 gas turbines. The fuels that are studied here are natural gas and enriched hydrogen fuel. The CFD models which are used in this work are an axisymmetric and a 3D model and the softwares are ANSYS CFX and ANSYS FLUENT. One of the main objectives of this thesis is the study of flame shape and NOx emission in hydrogen enriched combustion. In the first study of the present work, effect of adding hydrogen to non-preheated gas combustion was investigated and the results were compared with the available measurement data. Calculated laminar burning velocity with CANTERA showed a good agreement with the experimental and numerical references. Also, the accuracy of generated flamelet libraries in CFD tools to calculate adiabatic flame temperature was compared with different available tools. Results showed good agreement between available tools for the ranges of interest. In addition, flame shape and NOx prediction was studied in the gas turbine burner. Adding hydrogen to the fuel increased significantly turbulent burning velocity and OH distribution in the domain. The effect of hydrogen on the central stagnation point was studied and the simulation results did not show a significant effect on the stagnation point location. Beside the flame shape, this study showed that although the CFD NOx prediction tools in ANSYS CFX and ANSYS FLUENT predict the trend of NOx and the flame propagation in the right manner, in order to use as a reliable prediction tool in the gas turbine industry they need to be improved.