Experimental and numerical investigation of hydrogen injection, spontaneous ignition and flame stabilization in a lab-scale sequential combustor at high pressure

Sequential combustion staging has emerged as a well-suited approach for burning hydrogen in gas turbines, while maintaining low emissions and high cycle efficiency. A characteristic feature of sequential combustion systems is the high inlet temperature and the balance of flame propagation versus spontaneous ignition controlling flame stabilization in the second combustor stage. For the development of gas turbine combustion systems, able to operate on carbon-free fuels, it is important that experimental data at relevant conditions is available and that turbulent combustion models can accurately predict flame stabilization in the highly turbulent reacting flow. To match the propagation-to-auto-ignition balance, which is controlling flame stabilization, experimental validation of numerical models plays a key role in combustion systems development. Experimental results of N2-diluted hydrogen and pure hydrogen flames serve as a validation basis of Large-Eddy Simulations. Two flame stabilization configurations are investigated featuring significant differences in the steady-state flame location. Flame stabilization occurs in the combustor or directly at the fuel injection nozzle. The numerical model tested is able to capture the main flame-stabilization location observed in the experiments, while it is unclear whether the model correctly captures the occurrence of intermittent small ignition kernels in the mixing section.