Magnetic Stabilisation of Strained Hydrogen Flames
Exploring active control strategies via magnetic fields to stabilise thermodiffusive instabilities in lean-premixed hydrogen flames
F. Aziz (TU Delft - Aerospace Engineering)
Ivan Langella – Mentor (TU Delft - Flight Performance and Propulsion)
Nguyen Anh Khoa Doan – Graduation committee member (TU Delft - Aerodynamics)
Carlo Maria Servi – Graduation committee member (TU Delft - Flight Performance and Propulsion)
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Abstract
This thesis explores the magnetic stabilisation of strained hydrogen flames, focusing on mitigating thermodiffusive instabilities in lean premixed laminar hydrogen flames while preserving their inherent NOx reduction benefits. Utilising comprehensive numerical simulations of counterflow flame configurations, the study reveals that radially decreasing magnetic field gradients modify flame structure, predominantly through indirect mech-
anisms. These mechanisms involve magnetically induced alterations to the bulk flow field, which subsequently couple with differential diffusion effects to influence the distribution of reactants, affecting mixture fraction and the temperature field. Key findings demonstrate that the representative thermal thickness of the flame remains effectively unchanged, with a kernel-density (KDE) mode shift of 0.16 %. Crucially, total kinematic stretch is reduced by approximately 5-13 % near the axis, driven primarily by the curvature-induced contribution. Tangential strain exhibits a distinct two-regime response, decreasing by about 5-8 % in the preheat zone but increasing by 6-8 % in the reaction zone. Furthermore, a two-regime velocity-field redistribution is observed, where the axial component broadly weakens, while the radial velocity decreases for low progress variable (C) near the axis and strengthens for C ≳ 0.5. This research clarifies that direct magnetic effects are intrinsically weak and negligible
for practical control, with effective manipulation relying on these indirect pathways. The study also highlights that the efficacy of magnetic control diminishes with increasing strain rates and richer equivalence ratios. This work provides novel insights into the fundamental mechanisms governing magnetic control in premixed hydrogen flames, offering a framework for advancing sustainable combustion technologies.