CFD analysis on hydrogen combustion for aircraft gas turbine applications

The goal of the thesis is to investigate one of the possible solutions in the domain of emissions reduction and the process of decarbonization of aviation industry, by studying different configurations of novel combustors in aero gas turbine engines. In particular, the focus is on hydrogen combustion technology, replacing currently-used fossil fuels. After a consistent literature review on the state-of-art for hydrogen combustion, a hydrogen combustor typology is chosen and a specific geometry assessed for a first-approach study through computational fluid-dynamics simulations using the commercial software ANSYS Fluent. The geometry is placed in micromix combustors category, characterized by two main parts: an initial mixing zone and a combustion zone, with an overall length of seventy millimeters. Afterwards, a numerical model is built and validated, based on species transport model and a proper hydrogen-air chemical reaction mechanism in Chemkin format. With the results, some critical issues of hydrogen combustion, namely high temperatures, not-uniform flames, flashback, are addressed. Hence, by introducing variations on the combustor geometry, the influence of the selected parameters is highlighted. Among the other, a Venturi-tube before, and a coaxial injection air-hydrogen then, are introduced to the initial combustor model. Finally, it results that the flame structure is affected by these variations and a more suite solution, based on the specific needs of the design, could be handled by having an improved mixer-phase, a more uniform flame structure, lower temperatures and lower NOx emissions at the outlet.