Collective ignition characteristics of micron-sized iron particle streams

Iron exhibits significant potential as a carbon-free fuel, yet the collective ignition and combustion characteristics of the particle streams are poorly understood. This work experimentally investigates the ignition and combustion behaviors of micron-sized sponge iron particle streams in a multi-element diffusion flat-flame burner with precise control of the ambient conditions. Key parameters, including the ignition delay and particle temperature evolution are analyzed under varying temperatures and oxygen fractions. The results show that increasing oxygen fraction notably promotes ignition and raises particle temperatures, a trend that contrasts with single-particle ignition behavior. A statistical criterion based on 10% of the peak luminous intensity is adopted to define ignition delay, effectively capturing the collective ignition dynamics of particle ensembles. Finally, the study clarifies the distinct ignition mechanisms of particle streams, which may provide quantitative benchmarks for the modeling and design of iron-based combustion systems.