On the possible coexistence of two different regimes of metal particle combustion

Altman, Igor; Demko, Andrew R.; Hill, Kevin J.; Pantoya, Michelle L.

doi:10.1016/j.combustflame.2020.08.015

Cited by 15 publications

(19 citation statements)

References 17 publications

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“…The issue is related to the non-unimodal distribution of the burn time that is often masked by measurement scatter and selecting either the mean or the minimum/maximum burn time value. It is this bimodal distribution of the burn time that has led us to the conclusion of the coexistence of two different regimes of Al particle combustion [13]. Note that our observation of the bimodal burn time distribution is not isolated, although researchers just do not pay close attention to its occurrence [17,18].…”

Section: Burn Time Of Metal Particles: What We Really Get From Experi...mentioning

confidence: 70%

“…We believe that this knee inflection is enough to invalidate existing concepts and justify a need to revisit the fundamental physics that are the foundation of model development. Furthermore, recent evidence of two regimes of Al particle combustion characterized by noticeably different burn times [13] is probably the most pivotal result justifying further consideration of existing metal combustion models.…”

Section: Deficiencies In Current Concepts Of Metal Particle Combustionmentioning

confidence: 99%

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Comprehending Metal Particle Combustion: a Path Forward

Altman

Pantoya

2022

Propellants Explo Pyrotec

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The paper discusses the physics required for accurate modeling of metal particle combustion and includes aspects previously neglected. Specifically, three physical phenomena are emphasized: 1) internal boiling on the condensed oxide-metal interface; 2) condense-luminescent loss during nano-oxide formation; and, 3) suppressed heat transfer on the metal particle surface due to a low energy accommodation coefficient (EAC) are essential. The last two phenomena were explored in previous work. Internal particle interface boiling detailed in the current work enables the semi-heterogeneous combustion of Al particles, an im-portant process needing attention for accurate modeling. The interface boiling mechanism allowing for the semi-heterogeneous combustion explains a number of experimental puzzles related to metal particle combustion. In particular, the semi-heterogeneous combustion justifies the coexistence of two burning regimes of Al particles (slow and fast) recently observed. Based on reported findings, revising current numerical models for metal particle combustion to include these three physical phenomena is necessary. Implications toward enhancement of energetic performance for metal-containing formulations are also discussed.

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Section: Burn Time Of Metal Particles: What We Really Get From Experi...mentioning

confidence: 70%

Section: Deficiencies In Current Concepts Of Metal Particle Combustionmentioning

confidence: 99%

Comprehending Metal Particle Combustion: a Path Forward

Altman

Pantoya

2022

Propellants Explo Pyrotec

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“…Then, based on the data in Table 1 that shows a signi cant reduction in the mass fraction of α-alumina for SQ particles, the change in the combustion regime is evident. Note that the coexistence of two different combustion regimes for metal particles was discussed in [14]. The coexistence of two combustion regimes depends on the heat transfer at the interface between the particle surface and gas.…”

Section: Discussionmentioning

confidence: 99%

“…A comprehensive study investigating the relationship between nano-oxide occurrence and related radiant emission during metal combustion may shed light on a lot of puzzles unresolved to date. In particular, understanding the link between nano-oxide formation and energy release may explain the coexistence of two regimes for aluminum particle combustion recently reported [14]. Altman et al [14] showed the coexistence of fast and slow combustion regimes for Al particle oxidation that has extremely important implications to energetic applications.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, understanding the link between nano-oxide formation and energy release may explain the coexistence of two regimes for aluminum particle combustion recently reported [14]. Altman et al [14] showed the coexistence of fast and slow combustion regimes for Al particle oxidation that has extremely important implications to energetic applications. They showed that the different temporal character of heat transfer corresponds to different combustion regimes (i.e., a fast and slow regime), but the underlying cause of the temporal differences remains elusive.…”

Section: Introductionmentioning

confidence: 99%

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Direct Identification of Two Regimes of Metal Particle Combustion using Condense-luminescence

Tran¹,

Pantoya²,

Altman³

2021

Preprint

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Experiments were designed to investigate two regimes of metal particle combustion: fast and slow burning regimes. Stress-altering aluminum particles had been shown to produce a distinctly faster burning rate compared to untreated aluminum particles. The root cause for the differences in burning rate had been unclear. In this study, stress-altered and untreated aluminum particles were reacted as dispersed powder in a closed bomb calorimeter designed to monitor the transient temperature changes resulting from energy release upon combustion. The product residue was analyzed for size and species concentration. Results showed metastable γ-alumina that is associated with nano-oxide formation was in substantially higher concentration for stress-altered particle reactions that produced greater energy transfer rates. The increased energy transfer rate corresponded to higher radiant energy emission owing to condensation of nano-oxide particles. This study justifies condense-luminescence as a means for increasing the energy release rate of aluminum particles. By strategically altering metal fuels to control a formation of nano-oxide particles upon combustion, appreciable increases in the radiant energy flux can transform energy release rates.

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