Exploring the discrete and continuous flame propagation behavior of laminar iron flames

Metal powders, such as iron, are promising circular carrier of renewable carbon-free energy. However, little is known about the flame propagation behavior of metal particles such as iron. To develop practical largescale industrial energy-conversion technologies using iron particles, it is crucial to understand discrete flame propagation behavior. In this work, an Eulerian-Lagrangian simulation framework with point source particles was developed to study the laminar flame propagation behavior in pre-suspended iron particles in air, using a low-Mach code, Alya. Particles of various sizes and concentrations were used to perform the simulations, which provides insights into the discrete and continuous regimes of flame propagation. A discreteness parameter, X, is used to quantify this behavior. It was observed that for lower values of X(< 1), the flame propagation shows a discrete behavior and as keeps increasing, it becomes more continuous. The difference in propagation behavior was quantified by performing quasi-1-D and full 3-D simulations for the same conditions. The discreteness effect is more pronounced in larger particles than smaller ones for the same fuel-air ratios due to the greater inter-particle distances. These findings can be useful in designing industrial-scale burners, particularly for particle sizes and concentrations.