Energy Conversion Using Metal Combsution

Overview

Metals, such as Al, Fe, and Mg, are among the promising energy carriers due to their high volumetric energy density, abundant availability, carbon-free nature, and recyclability through oxide reduction processes. Owing to their strong reducing ability, some metals can react even with low-reactive oxidizers, reducing H2O and CO2 into H2 and CO, respectively. Consequently, metal combustion for heat production can simultaneously serve as a pathway for generating feedstocks for carbon-neutral fuels, which can be further synthesized via processes such as methanation. Nevertheless, metal combustion has mainly been investigated in the context of dust explosions or propulsion, and a fundamental understanding of combustion processes remains insufficient, particularly under different oxidizing environments.

Concept of metal-based energy conversion

Spatially-fixed single particle combustion using ultrasonic levitation

Investigating the combustion of a single metal particle without flame propagation is essential for understanding the fundamental phenomenological behavior of metal combustion. In previous studies, freely falling, wire-suspended, or electromagnetically fixed particles have typically been employed; however, such approaches are highly susceptible to external disturbances, which can disrupt the fluid-dynamical, thermal, and kinetic boundary conditions of the combustion process.

In this study, we propose a spatial fixation method based on acoustic levitation generated by ultrasonic waves. A particle is spatially fixed in a stationary acoustic field formed by an array of ultrasonic transducers, ignited using a focused laser, and its temporal combustion evolution is observed using high-speed, time-resolved imaging. In addition, spectroscopy and laser-induced fluorescence (LIF) measurements are employed to quantify the temporal and spatial distributions of major intermediates, thereby providing detailed insights into the combustion kinetics of metal particles.

Schematic of the experimental setup and photograph of the levitated Al particle (J. Mitsumata et al., 2026)


Flash-ignited nanoparticle combustion under different oxidizing environments

When metals are fabricated as nanoparticles, their high surface-to-volume ratio and reduced melting point enable efficient photothermal ignition using a high-intensity flash. Due to the decreased particle diameter, the combustion process becomes increasingly governed by chemical kinetics, which suppresses the influence of diffusive transport on flame behavior. We have developed a chamber system that allows the ignition of metal nanoparticles under well-controlled oxidizing environments. The resulting flame behavior is observed using high-speed imaging combined with two-color pyrometry, enabling quantitative evaluation of metal reaction kinetics under various oxidizing conditions.

Flash-ignited Aluminum nanoparticle flames (K. Ajisaka et al., 2026)


Modeling of single particle combustion

Metal combustion is inherently complex, and as a result, previous numerical studies have often treated chemical kinetics, phase change, and heat/mass transfer as decoupled processes. In this study, we develop an integrated numerical framework capable of quantitatively describing the strong coupling among these phenomena. A thermal-fluid analysis framework is established to dynamically track gas-liquid interfaces using the Volume-of-Fluid (VOF) method while handling phase changes. Furthermore, by implementing detailed reaction kinetics within OpenFOAM, the coupled analysis of phase changes and chemical reactions in a single particle becomes possible, allowing systematic investigation of particle-size effects and reaction kinetics across different metal and oxidizer types. The validity of the model will be verified through direct comparison with the aforementioned experiments, with the ultimate goal of establishing a comprehensive and predictive understanding of metal particle combustion.

Temperature distribution of a burning Al particle computed on an adaptive mesh (H. Jiang et al., 2025)


Collaborators:
Prof. Alberto Cuoci (Politecnico di Milano)
Prof. Wookyung Kim (Hiroshima University)
Profs. Yutaka Tabe and Suguru Uemura (Hokkaido University)

Recent Reports

Combustion of Al wire

  • M. Lee and Y. Suzuki,
    “Study on the effect of oxidizing atmospheres on ignition temperature of Aluminum,”
    61st National Heat Transfer Symposium of Japan, Kobe, Japan, May. 29-31, (2024), C223.
  • M. Lee, K. Uezono, and Y. Suzuki,
    “Study on combustion process of aluminum wires in different oxidizing atmospheres,”
    60th National Heat Transfer Symposium of Japan, Fukuoka, Japan, May 25-27, (2023), F131.

Modeling of particle combustion

  • Jiang, H., Lee, M., Cipriano, E., Caraccio, R., Cuoci, A., and Suzuki, Y.,
    “Numerical Investigation of Surface Reactions in Aluminum Particle Combustion Under Various Oxidizing Conditions,”
    Renewable Metal Fuels (ReMeF) Symposium, Rapperswil, Switzerland, Poster #9, (2025).
  • Jiang, H., Lee, M., Cipriano, E., Caraccio, R., Cuoci, A., and Suzuki, Y.,
    “Numerical Investigation of Surface Reaction Influences on Aluminum Particle Combustion Under Various Oxidizing Conditions,”
    62nd NHTS/HTSJ Int. Heat Transf. Symp., Okinawa, Japan, IOS7-3-04, (2025).
  • Lee, M., Saeki, R., and Kim, W.,
    “Numerical Study of Hydrogen Addition Effects on Aluminum Particle Combustion,”
    J. Energy Inst., Vol. 105, (2022), pp.72-80.
    (doi:10.1016/j.joei.2022.07.009)

Last update: 2026-01-22