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Light extinction and scattering to determine nanoparticle formation rates during droplet jetting in aluminum dust flames

Jüngst, Niklas LU ; Wu, Zhiyong LU orcid ; Ruan, Can LU ; Aldén, Marcus LU and Li, Zhongshan LU (2025) In Powder Technology 453.
Abstract

The combustion of aluminum powder enables a CO2-free generation of heat and electricity. To understand the asymmetric combustion of burning aluminum particles, we imaged light extinction and scattering with high speed and magnification. In the flame, particles melt, ignite, and build up a spherical flame sheet of condensed-phase alumina around the droplet. Shortly thereafter, the asymmetric stage occurs where the flame locally extinguishes, the droplet accelerates, i.e., droplet jetting, and leaves behind a condensation trail of alumina particles. Two alternately pulsed LEDs were used to image light extinction and scattering in the condensation trail at 200000 frames per second. This yields quasi-simultaneous images of... (More)

The combustion of aluminum powder enables a CO2-free generation of heat and electricity. To understand the asymmetric combustion of burning aluminum particles, we imaged light extinction and scattering with high speed and magnification. In the flame, particles melt, ignite, and build up a spherical flame sheet of condensed-phase alumina around the droplet. Shortly thereafter, the asymmetric stage occurs where the flame locally extinguishes, the droplet accelerates, i.e., droplet jetting, and leaves behind a condensation trail of alumina particles. Two alternately pulsed LEDs were used to image light extinction and scattering in the condensation trail at 200000 frames per second. This yields quasi-simultaneous images of transmission and scattered light. The geometry of the light-scattering experiment and Mie theory yield the collection efficiency of scattered light as a function of the particle size. An iterative calculation of the collection efficiency and the single-scattering albedo, the ratio of scattering and extinction, converges and yields the particle diameter in the Rayleigh regime. The correction for total scattered-light in the extinction yields the absorbance from which the nanoparticle volume is derived. Nanoparticles appear at the onset of the trails near the droplet and grow along the trail from around 40 nm to 110 nm until they are outside the Rayleigh regime. The nanoparticle formation rate is 50 % of the total alumina formation rate during the symmetric phase. The large occurrence frequency of droplet jetting makes it an important contribution to nanoparticle formation and to the total heat release in aluminum combustion.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aluminum dust flame, Droplet jetting, High-speed imaging, Light extinction and scattering, Nanoparticles
in
Powder Technology
volume
453
article number
120633
publisher
Elsevier
external identifiers
  • scopus:85215098571
ISSN
0032-5910
DOI
10.1016/j.powtec.2025.120633
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 The Authors
id
b0089962-6cf0-49c3-9874-0ec6aed90152
date added to LUP
2025-01-27 09:03:43
date last changed
2025-04-04 14:46:03
@article{b0089962-6cf0-49c3-9874-0ec6aed90152,
  abstract     = {{<p>The combustion of aluminum powder enables a CO<sub>2</sub>-free generation of heat and electricity. To understand the asymmetric combustion of burning aluminum particles, we imaged light extinction and scattering with high speed and magnification. In the flame, particles melt, ignite, and build up a spherical flame sheet of condensed-phase alumina around the droplet. Shortly thereafter, the asymmetric stage occurs where the flame locally extinguishes, the droplet accelerates, i.e., droplet jetting, and leaves behind a condensation trail of alumina particles. Two alternately pulsed LEDs were used to image light extinction and scattering in the condensation trail at 200000 frames per second. This yields quasi-simultaneous images of transmission and scattered light. The geometry of the light-scattering experiment and Mie theory yield the collection efficiency of scattered light as a function of the particle size. An iterative calculation of the collection efficiency and the single-scattering albedo, the ratio of scattering and extinction, converges and yields the particle diameter in the Rayleigh regime. The correction for total scattered-light in the extinction yields the absorbance from which the nanoparticle volume is derived. Nanoparticles appear at the onset of the trails near the droplet and grow along the trail from around 40 nm to 110 nm until they are outside the Rayleigh regime. The nanoparticle formation rate is 50 % of the total alumina formation rate during the symmetric phase. The large occurrence frequency of droplet jetting makes it an important contribution to nanoparticle formation and to the total heat release in aluminum combustion.</p>}},
  author       = {{Jüngst, Niklas and Wu, Zhiyong and Ruan, Can and Aldén, Marcus and Li, Zhongshan}},
  issn         = {{0032-5910}},
  keywords     = {{Aluminum dust flame; Droplet jetting; High-speed imaging; Light extinction and scattering; Nanoparticles}},
  language     = {{eng}},
  month        = {{03}},
  publisher    = {{Elsevier}},
  series       = {{Powder Technology}},
  title        = {{Light extinction and scattering to determine nanoparticle formation rates during droplet jetting in aluminum dust flames}},
  url          = {{http://dx.doi.org/10.1016/j.powtec.2025.120633}},
  doi          = {{10.1016/j.powtec.2025.120633}},
  volume       = {{453}},
  year         = {{2025}},
}