Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6629981 | Fuel | 2018 | 8 Pages |
Abstract
Ignition by a pre-chamber generated hot jet is a promising technology to reduce NOx emissions through extending lean burn limits. However, the role of the pre-chamber fuel reactivity in the main chamber ignition still remains unclear. In the present study, effects of the pre-chamber fuel reactivity on ignition of mixture in a main chamber by the hot jet, which is generated by the combustion of syngas in the pre-chamber, are numerically investigated. In the investigation, different ratios of CO/H2 of syngas are considered under a thermally-equal condition. CFD simulations are performed using the code based on the KIVA-3V release 2 program coupled with an in-house developed chemical solver. A detailed chemical kinetics mechanism with 15 species and 41 reactions is adopted for the hydrogen and syngas oxidation. The hot jet ignition delay time is characterized by the maximum rate-of-change of the pressure in the main chamber. For the combustion initiation process, three stages are identified: ignition stage (stage I), flame development stage (stage II), and flame propagation stage (stage III). Significant effects of fuel reactivity are only observed on stage I that the ignition delay time considerably increases with increasing CO/H2 ratio. Further analyses of the local temperature of the hot gas and some important elementary reactions indicate that the low reaction rate of carbon monoxide oxidation (R22: COâ¯+â¯OHâ¯=â¯Hâ¯+â¯CO2) causes incomplete fuel conversion in the orifice due to insufficiently available time for the reactions . The fuel conversion analysis confirms that the small-diameter orifice effect is the main reason for hot jet temperature drops under low pre-chamber syngas reactivity conditions, exhibiting as inhibiting effects on stage I.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Nana Wang, Jinxiang Liu, Wayne L. Chang, Chia-fon F. Lee,