Effect of magnetic force on intrinsic instabilities in lean hydrogen flames
V. Mysore Natesh (TU Delft - Aerospace Engineering)
I. Langella (TU Delft - Aerospace Engineering)
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Abstract
Controlling intrinsic flame instabilities in lean premixed hydrogen flames is central to stable, efficient, and low-emission operation. This study assesses whether steady magnetic-field gradients can be used to control the growth of intrinsic flame instabilities. For this purpose, two-dimensional high-fidelity laminar simulations are performed for a lean hydrogen-air flame, with full chemistry and constant magnetic-field gradients applied along and against the streamwise direction. A linear stability analysis is first carried out to examine how the imposed magnetic forcing modifies perturbation growth through the corresponding dispersion relation. The analysis shows that a negative streamwise magnetic-field gradient weakens the long-wavelength branch associated with hydrodynamic instability. The nonlinear flame dynamics are then examined, showing that when the magnetic-field gradient is applied opposite to the flow, global flame wrinkling is reduced by about 22% at |∇(B
2)|=3000T
2m
−1, while the stretch factor and the super-adiabatic temperature remain nearly unchanged. Moreover, it is observed that the magnetic gradient triggers the generation of counter-rotating vortical structures that oppose the Darrieus-Landau instability, while the thermodiffusive instability remains unaffected. The mechanism underlying this behaviour is explained in the paper. Magnetic fields thus offer a contactless means to modulate instability growth in premixed hydrogen flames and provide a physics-based framework for future stability control strategies. Novelty and significance statement: This work demonstrates, for the first time, the use of magnetic-field gradients to control the growth of intrinsic flame instabilities (IFI) in lean premixed hydrogen flames. It identifies the hydrodynamic (Darrieus–Landau) mode as the instability suppressed by the forcing and explains the mechanism responsible for this response. The underlying physics remains largely unexplored, yet it is directly relevant to next-generation hydrogen combustors where instability control is a key requirement. The results help identify a relevant gradient range and indicate effective in-flame placement strategies for targeted experiments and early design studies.
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