In-situ measurement of spectral emissivity of aluminum flame combustion products using saturated atomic lines of alkali metals
Notice bibliographique
Résumé
Aluminum combustion occurs at extremely high temperatures, exceeding those of typical hydrocarbon flames by over 1000 K. Due to high temperatures and the condensed nature of metal combustion products, radiation heat transfer is often expected to play a dominant role in aluminum flames, as predicted by many theoretical models. Paradoxically, however, no definitive experimental evidence has confirmed these predictions. To reconcile theory with reality, accurate radiation heat transfer models require reliable radiative properties of combustion products at high temperatures and for sub-micron particle sizes. However, direct measurement of the emissivity of high-temperature aluminum combustion products in flames is particularly challenging and requires complex calibration procedures. This paper introduces a novel method for measuring the absolute spectral emissivity of high-temperature combustion products in-situ . The method is calibration-free and instrumentally simple, and is based on the comparison of the intensity of the continuum spectra emitted by the condensed combustion products and the intensity of saturated atomic lines of alkali metals. The intensity of the saturated atomic lines reaches the intensity of a blackbody, and depends only on temperature. Line saturation is achieved by adding less than 2% of the corresponding alkali metal chloride (LiCl, NaCl, KCl, RbCl, CsCl) to powdered aluminum fuel. Measurements of the emissivity of the condensed products from aluminum Bunsen dust flames within the 589–852 nm spectral range reveal strikingly low spectral emissivity values on the order of ϵ λ ∼ 0.02–0.03, which is more than an order of magnitude below values typically assumed in most theoretical models. The obtained results align with Mie theory predictions for an optically thin aluminum oxide nanoparticle cloud. The potential applications of the proposed diagnostic technique extend well beyond metal combustion—for example, to non-reactive particles seeded to hydrocarbon flames, flame-synthesized nanoparticles, and dusty plasmas—and can be leveraged not only to determine spectral emissivity of condensed-phase species, but also the temperature of the gas medium. Novelty and significance statement This paper presents a novel calibration-free technique to measure the absolute spectral emissivity of the condensed-phase species in flames. The new technique is used to measure, for the first time, the absolute spectral emissivity of high-temperature aluminum oxide combustion products. These measurements are needed for theoretical modeling to properly quantify the role of radiation heat transfer in metal flames, and rectify the apparent disconnect between theoretical predictions and available experimental data. The derived insights elucidate many common misconceptions regarding the optical properties of the condensed emitters in aluminum flames, which have far reaching implications in metal flame modeling and pyrometric measurements.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».