Session: 04-45 Combustion dynamics - modeling III

Paper Number: 127332

127332 - Flashback Prevention in a Hydrogen-Fueled Reheat Combustor by Water Injection Optimized With Global Sensitivity Analysis 

Hydrogen-powered gas turbines have emerged as a key technology in the pursuit of net-zero carbon emissions because of their ability to produce clean, carbon-free energy. However, the hydrogen flame is characterized by its tendency to flashback, a phenomenon that has the potential to damage injector and other engine components. In addition, the relatively high amount of NOx produced during hydrogen combustion implies the need for alternative approaches to reduce emissions. In this context, water injection has re-emerged as a promising solution.

This paper presents an in-depth investigation of the effects of water injection within a simplified version of the Ansaldo Energia GT36 gas turbine combustion system, characterized by its state-of-the-art sequential combustion technology. The investigation is carried out under realistic operating conditions, simulating pressures of 20 atmospheres and using Large Eddy Simulation (LES) coupled with the Thickened Flame Model (TFM) and an adaptive mesh refinement. The water injection conditions are optimized by performing a parametric study based on global sensitivity analysis and a surrogate model using Gaussian process is employed as a way to reduce computational cost. In particular, the influence of four design parameters, namely the Sauter mean diameter, the mass flow and the external and thickness angle of the spray’s hollow cone, on the system performance, is tested to achieve an optimized solution. In the ‘dry’ case, the LES simulations show several flashback events, which are a defining aspect of the considered conditions. These flashback events are attributed to compressive pressure waves resulting from autoignition in the core flow and to the proximity to the mixture’s characteristic crossover temperature. The use of water injection is found to be effective in suppressing the flashback occurrence. In particular, the global sensitivity analysis shows that the external angle of the spray cone and the mass flow of water are the most important design parameters for flashback prevention. Moreover, NOx was shown to be reduced by about 17% by the use of the water injection at the tested conditions.

Once an optimised condition with water injection is found, a recently proposed method to downscale the combustor to lower pressures is applied and tested. Two additional LES are performed for this purpose at the ‘dry’, unstable condition and the ‘wet’, stable condition. The results show that similar dynamics, respectively unstable and stable, is predicted at 1 atm, suggesting the robustness of the method. This provides avenues for experimentally testing combustion dynamics at simplified conditions which are still representative of high-pressure practical configurations.

Presenting Author: Pablo Rouco Pousada TU Delft

Presenting Author Biography: Pablo Rouco obtained his BSc at the University of Vigo (2021) and his MSc at the Carlos III University (2023). During his BSc, he published a paper in MDPI Aerospace on the optimisation of the design of a multistage rocket and its trajectory. In the same year, he was ranked in the top 19 in the National Ranking of Graduates 2021 in Aerospace Engineering by the Spanish Society of Academic Excellence. As part of his MSc studies, in 2023 he joined the TU Delft Flight Performance and Propulsion Department to write his Master's thesis, which involved the study of a hydrogen-fuelled reheat combustor with water injection. A flashback analysis and an optimisation using global sensitivity analysis was performed. He is currently a future PhD candidate at TU Delft. His research interests include hydrogen combustion, optimisation and CFD.

Authors:

Pablo Rouco Pousada TU Delft
Nguyen Anh Khoa Doan TU Delft
Konduri Aditya Indian Institute of Science
Michael Duesing Ansaldo Energia
Andrea Ciani Ansaldo Energia
Ivan Langella TU Delft