Experimental investigation of partially premixed combustion in a DISI natural gas engine: Emissions behaviour
Notice bibliographique
Résumé
Experimental results of partially premixed combustion using direct injection of natural gas during the compression stroke in a spark ignited single cylinder research engine are presented. A constant overall 0.70 equivalence ratio was used, with 34 and 69 kPa gauge intake pressures. Two injector nozzle designs were employed, one with a flat injection plane and one with a narrower 100 degree injection cone. Injection timing was varied to change the degree of premixing, from fully premixed with injection near BDC, to stratified combustion with injection near TDC. The effects on engine-out emissions of NO, CO, unburnt hydrocarbons, and particulate matter were assessed, along with the combustion efficiency determined from exhaust gas composition. Later injection timings resulted in reduced time for mixing before ignition, concentrating the fuel mass and increasing the local equivalence ratios of combustion. Unburnt hydrocarbon levels decreased with later injection timings as the fuel concentrated and injection was directed into the piston bowl. NO increased as local equivalence ratios approached stoichiometric, before reducing at richer local equivalence ratios. Late injection timings resulted in order of magnitude increases in CO and particulate matter as the low mixing time resulted in combustion at high local equivalence ratios. Combustion efficiency reached a maximum at moderate degrees of premixing. The residence time of the fuel between the end of injection and ignition was found to be a critical metric in defining the resulting emissions. The cone nozzle confined the fuel to the piston bowl at earlier injection timings, resulting in lower unburnt hydrocarbon emissions. Operation at 66 CAD BTDC injection timing and 34 kPa gauge intake pressure (giving 34.2 CAD of residence time) with the cone nozzle was found to give the optimal emissions profile. Unburnt hydrocarbon emissions decreased by 73.8%, but CO levels increased by a factor of 7.5 from 1338 to 11 443 ppm compared to fully premixed operation with injection near BDC. NO levels were moderate at 612 ppm, and particulate matter emissions increased moderately to 5.6E+06 #/cm 3 , compared to the motored concentration of 3.1E+05 #/cm 3 . The combustion efficiency of 90.3% was moderate in comparison to other operating points. • Later injections during compression stroke gave higher spatial fuel concentration. • NO emissions increased with combustion locally near stoichiometric. • Hydrocarbon emissions fell with fuel concentration and lower crevice penetration. • Overly late injections resulted in high CO and particulate matter emissions. • Smaller included angle injector confined fuel more at earlier injection timings.
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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 | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 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 | 0,000 |
| 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 ».