A numerical study on effects of pre-chamber syngas reactivity on hot jet ignition

Nana Wang, Jinxiang Liu, Wayne L. Chang, Chia fon F. Lee

Research output: Contribution to journalArticlepeer-review

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: CO + OH = H + 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.

Original languageEnglish (US)
Pages (from-to)1-8
Number of pages8
JournalFuel
Volume234
DOIs
StatePublished - Dec 15 2018

Keywords

  • CO/H ratio
  • Fuel conversion
  • Hot jet ignition
  • Ignition delay time
  • Syngas reactivity

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry

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