CFD Analysis of a Lean Premixed Gas Turbine Combustor for H2 Applications

The present master’s Thesis was carried out in a collaboration between the Polytechnic of Turin and Ethos Energy Spa, both located in Turin, TO, Italy. The current state of power generation through natural gas cannot be abandoned or replaced without significant investment. This study arises from the need for redesigning a natural gas injector into one compliant with hydrogen-natural gas blends. Since the Paris Agreement of 2016, hydrogen has become of interest as an alternative fuel. Due to its efficient and clean combustion, hydrogen can be considered a valuable energy carrier in power generation. Considering the world's tendency to reduce emissions, the study is focused on NOx generation. Using 3D Computational Fluid Dynamics (CFD) tools in Ansys Fluent, the annular combustion chamber of a power-generating gas turbine plant is analyzed by comparing several fuel compositions from solely natural gas to an HCNG blend. The main developments of this study are in the context of the modification of the boundary conditions of the CFD model. The effects of the change in fuel mixture are studied in detail. This work aims at improving an existing model previously developed by modifying two boundary conditions. The first one is the coupling between the injector model and the combustion chamber model. The use of periodic modeling of the boundary conditions delivers a domain that needs to be reconstructed to achieve the coupling. This boundary reconstruction is achieved using an in-house routine developed in MATLAB. The second boundary condition consists of the introduction of an effusion cooling model. Originally modeled as a simple cooling stripe, the new model adopts a uniform injection region which can reproduce with great accuracy the effusion cooling and the interaction between the chamber and the liner. The result of the present study lays the foundations for the redesign of other existing systems. Through an upgraded design it will be possible to guarantee reliable performance for the machine also when switching to different HCNG blends, extending the life of the power plant.