Session: 04-29 Hydrogen II

Submission Number: 178930

Large Eddy Simulation of Hydrogen Reheat Flames Stabilized in a Lab-Scale Sequential Combustor at High Pressure 

Operating state-of-the-art gas turbines with 100% hydrogen using Dry Low Emission (DLE) premixed combustion technology offers a clean and efficient pathway toward a resilient and cost-effective low-carbon energy system. However, growing evidence shows that under typical gas turbine conditions—characterized by high reactant pressures and temperatures—thermo-diffusive instabilities can significantly enhance the turbulent burning rate of premixed hydrogen–air flames. This leads to major, yet unresolved, challenges in maintaining flame stability and minimizing NO_x emissions. In this context, theoretical analyses of hydrogen combustion fundamentals, supported by extensive experimental and numerical data, indicate that these thermo-diffusive instabilities are markedly mitigated under reheat combustion conditions in sequentially staged systems, suggesting the further development of this technology to optimally operate with 100% hydrogen at the most demanding (H-class) firing conditions. Therefore, accurately assessing the capability of numerical models to predict the spontaneous ignition and stabilization of hydrogen premixed flames in realistic burners under reheat conditions is a crucial step toward the timely and cost-effective development of zero-carbon gas turbine technologies.

To this end, the present study employs a series of high-pressure experiments conducted on a simplified, yet realistic, sequential combustion system fueled with both nitrogen-diluted and pure hydrogen to validate high-resolution numerical simulations. These simulations couple a standard Large Eddy Simulation (LES) turbulence model with a Partially Stirred Reactor (PaSR) approach incorporating detailed chemical reaction kinetics. Results from the LES/PaSR computations demonstrate that the model can correctly capture nominal operating conditions in which the partially-premixed reheat hydrogen flame stabilizes within the sequential combustion chamber. However, the model does not accurately reproduce the experimentally observed transition between the partially-premixed flame stabilized in the combustion chamber and the (off-design) non-premixed flame attached to the fuel injector. Therefore, a sensitivity analysis of the LES/PaSR model to variations in hot-gas (oxidizer) temperature—the key parameter governing flame stabilization in reheat systems—is conducted revealing both the current model’s limitations and potential pathways for its improvement.

Presenting Author: Andrea Gruber SINTEF

Presenting Author Biography: Andrea Gruber holds a doctoral degree in Mechanical Engineering from NTNU (2006), he is Senior Research Scientist at SINTEF Energy Research and Adjunct Professor at NTNU. His research interests span from fundamental research on turbulent-chemistry interaction in carbon-free fuels to applied research in the development of fuel-flexible stationary gas turbines: design and optimization of fuel injection systems, flashback prediction and control, static and dynamic flame stabilization in conventional and staged combustors.

Authors:

Andrea Gruber SINTEF
Ole Meyer SINTEF
Wonsik Song SINTEF
Joshua Gray DLR
Peter Griebel DLR
Birute Wood Ansaldo Energia Switzerland
Michael Duesing Ansaldo Energia Switzerland
Andrea Ciani Ansaldo Energia Switzerland