Laminar flame speed of jet fuel surrogates and second generation biojet fuel blends
Notice bibliographique
Résumé
An understanding of the fundamental combustion properties of alternative fuels is essential for their adoption as replacements for non-renewable sources. In the aviation industry, a promising candidate is hydrotreated renewable jet fuel (HRJF). HRJF can be synthesized in a sustainable and economically viable manner from long chain fatty-acid methyl esters found in jatropha and camelina seed, and the laboratory-scale characterization of the combustion properties of HRJF is an active area of research. Such research is motivated, in part, by the chemical complexity of biojet fuels which are composed of hundreds of hydrocarbon species, similar to conventional aviation grade fuels. The laminar flame speed has been identified as an important combustion parameter for many combustion applications, and is especially relevant to the aviation community. The laminar flame speed is also an important parameter in the validation of chemical kinetic mechanisms, as it is representative of the chemical reactivity of the fuel. In this study, laminar, atmospheric pressure, premixed stagnation flames were used to determine the laminar flame speed of HRJF blended in varying ratios with Jet A-1 aviation fuel, requiring a combination of experimental and numerical methods. Jet A-1 was also studied to allow for comparative benchmarking of the biojet blends. Experiments were carried out in a jet-wall stagnation flame geometry at a pre-heated temperature of 400 K. Centerline velocity profiles were obtained using particle image velocimetry, from which the strained reference flame speeds were determined. Simulations of each experiment were carried out using the CHEMKIN-PRO software package together with a detailed chemical kinetic mechanism, with the specification of necessary boundary conditions taken entirely from experimental measurements. A direct comparison method was used to infer the true laminar flame speed from the experimental and numerical strained reference flame speeds. In order to model the chemical kinetics of Jet A-1 and the biojet blends, it was necessary to identify a surrogate blend that emulates the reactivity of the biojet fuels, while consisting of a much smaller number of pure compounds. Published data shows significant discrepancies for many jet fuel surrogate components, motivating their inclusion in this study. Thus, laminar flame speeds were also obtained for three candidate jet fuel surrogate components: n-decane, methylcyclohexane and toluene, which are representative of the alkane, cycloalkane and aromatic components of conventional aviation fuel, respectively. Results for the pure surrogate components were used to generate a suitable surrogate blend for the biojet blends. The results form this work resolve conflicting laminar flame speed data for the surrogate components, which is essential for the further development of chemical kinetic mechanisms and contributes to the surrogate modelling of jet fuel combustion. The laminar flame speeds of the biojet blends are compared to the Jet A-1 benchmark over a wide range of equivalence ratios. The biojet blends are found to behave similarly to Jet A-1 for low to moderate levels of blending, but show a marked disagreement otherwise.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».