Effects of Gasoline Composition on Compression Ignition in a Motored Engine
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Notice bibliographique
Résumé
This study presents a fundamental investigation of gasoline autoignition behavior in a compression ignition engine, which is of great importance for next generation engine designs that employ low temperature combustion strategies. A total of eleven full boiling range gasolines with different octane number and sensitivity have been tested in a motored engine and a constant volume combustion chamber at various pressures, temperatures, and oxygen concentrations. For quantification of intermediate temperature heat release (ITHR), a new method was applied to the engine data by examining the maximum value of the second derivative of heat release rate. Combustion phasing comparisons of single-stage ignition fuels with various octane sensitivity showed that fuel with less octane sensitivity became more reactive as intake temperature and simulated exhaust gas recirculation (EGR) ratio decreased, while fuel with higher octane sensitivity had a reverse trend. When low temperature heat release (LTHR) was not active, the amount of ITHR increased as the intake temperature and oxygen mole fraction increased. These ITHR trends, depending on octane sensitivity, were almost identical with the trends of combustion phasing, showing that ITHR significantly affects fuel autoignition reactivity and determines octane sensitivity. In addition, the strong dependence of ITHR on equivalence ratio enhanced the ϕ-sensitivity. For the similar combustion phasing, the higher octane sensitivity fuels exhibited faster rise rates of ITHR intensity than the lower octane sensitivity fuels, leading to more advanced hot-ignition phasing with increasing equivalence ratio. For two-stage ignition fuels, LTHR significantly enhanced ITHR, eventually advancing the autoignition timing. Both LTHR and ITHR were suppressed by increasing the simulated EGR ratio. The intake pressure boosting increased LTHR whereas the magnitude of ITHR for fuels with a lower research octane number (RON), which exhibited a great amount of ITHR, became saturated as the intake pressure increased. However, the average ITHR per crank angle increased with the intake pressure, showing concise and strong intermediate temperature reaction. With regard to physical property effects, higher aromatic content led to lower volatility and higher density, resulting in a slower liquid fuel evaporation process. The physical ignition delay was very sensitive to air temperature whereas oxygen dilution rarely affected the physical ignition delay. With regard to chemical property effects at the same RON, fuel with a higher aromatic content was more resistant to autoignite at high pressure and less sensitive to the oxygen dilution whereas the alkane-rich fuel was less sensitive to the temperature due to pronounced negative temperature coefficient (NTC) behavior. For the same RON and octane sensitivity, fuel with a higher amount of n-alkane was less sensitive to the oxygen dilution.
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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 | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| 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 | 0,001 |
| 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 découle