Quantification of the size, 3D location and velocity of burning iron particles in premixed methane flames using high-speed digital in-line holography

摘要

Due to its low emission and high energy density, iron powder has been proposed as a promising recyclablemetal fuel for a future low-carbon society. The comprehensive understanding of combustion behaviorof iron particles is crucial for studying fundamental mechanisms, developing suitable combustiontechnologies, and designing efficient iron powder combustor. In this work, iron particles are combusted ina modified Bunsen burner with a stable metal powder supplying system. As a versatile three-dimensional(3D) imaging technique, high-speed digital in-line holography (DIH) is employed to reconstruct the 3Dparticle field and simultaneously quantify the size, 3D location and velocity of burning iron particles. Thestatistical results of three cases with oxygen volume fraction varying from 24 to 40 are obtained andcompared at different heights above the burner. Along the height, some typical features of the burningiron particles were observed. The violent combustion of iron particles accelerates the ejection of the particlesradially outward from the central region of the flame, resulting in non-uniform spatial distributionof the particles and reducing the particle number density in the measurement volume. Such trend is enhancedwith increased oxygen concentration. Besides, the observed particle size enlarged as the heightincreases, which validates the swelling phenomenon of iron particle oxidation. The results demonstratethat DIH is a powerful tool for in-situ, quantitative characterization of particle dynamics in flames.