High-fidelity numerical modeling and design of hydrogen burners for aero engine applications

Hydrogen has recently gained attention as a promising alternative to conventional aviation fuels with the objective of achieving net-zero CO2 emissions by 2050. Despite growing investments by leading aerospace companies, the transition to hydrogen-powered aircraft still faces challenges, particularly in hydrogen sustainable production, storage, and utilization. This thesis work focuses on the latter, specifically on hydrogen combustion in aero engine gas turbines, through the development of high-fidelity numerical methodologies for modeling turbulent hydrogen/air flames in non-premixed systems, and through the design of an innovative 100% hydrogen burner for aero engine application. The first key contribution of the study is the development of a regularized DTFLES formulation, which extends the model’s applicability to multi-regime combustion. Compared to existing formulations, the novel approach prevents the onset of artificial discontinuities, inherently addresses the desynchronization between artificial modifications of flame thickness and mixture reactivity, and ensures at least a continuous evolution of this parameter while retaining the computational efficiency of the standard methodology. The approach is implemented in the commercial CFD solver ANSYS Fluent 2023R1 and compared against the state-of-the-art formulation through LES simulations of hydrogen/air flames across different levels of complexity. The agreement with available experimental data is excellent, confirming that the novel methodology does not compromise the accuracy of existing models while preventing abrupt modifications of their parameters in both space and time. The second key contribution is the numerical design of a novel non-premixed 100% hydrogen lean burner for aero engine application. The burner stabilizes the flame through a coaxial triple-swirler injector that is numerically designed and investigated under representative engine conditions, and subsequently scaled to match the constraints of the atmospheric reactive test rig installed at the University of Florence. An investigation under atmospheric pressure conditions is conducted, exploiting the proposed numerical methodology, revealing a lifted multi-regime flame. The dominant formation of thermal NO, mainly originating from the diffusion-controlled secondary flame front, is predicted by a dedicated post-process. This last result remains preliminary, as the analysis is conducted under adiabatic conditions, and heat losses could significantly impact NO production rates. The findings support the burner commissioning and contribute to the preliminary design of future hydrogen combustion technologies, advancing next-generation aero engine solutions.