Damköhler number effects on soot formation and growth in turbulent nonpremixed flames

Antonio Attili, Fabrizio Bisetti, Michael E. Mueller, Heinz Pitsch

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

The effect of Damköhler number on turbulent nonpremixed sooting flames is investigated via large scale direct numerical simulation in three-dimensional n-heptane/air jet flames at a jet Reynolds number of 15,000 and at three different Damköhler numbers. A reduced chemical mechanism, which includes the soot precursor naphthalene, and a high-order method of moments are employed. At the highest Damköhler number, local extinction is negligible, while flames holes are observed in the two lowest Damköhler number cases. Compared to temperature and other species controlled by fuel oxidation chemistry, naphthalene is found to be affected more significantly by the Damköhler number. Consequently, the overall soot mass fraction decreases by more than one order of magnitude for a fourfold decrease of the Damköhler number. On the contrary, the overall number density of soot particles is approximately the same, but its distribution in mixture fraction space is different in the three cases. The total soot mass growth rate is found to be proportional to the Damköhler number. In the two lowest Da number cases, soot leakage across the flame is observed. Leveraging Lagrangian statistics, it is concluded that soot leakage is due to patches of soot that cross the stoichiometric surface through flame holes. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames.

Original languageEnglish (US)
Pages (from-to)1215-1223
Number of pages9
JournalProceedings of the Combustion Institute
Volume35
Issue number2
DOIs
StatePublished - Jan 1 2015

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

Keywords

  • Damköhler number effects
  • Direct numerical simulations
  • Soot
  • Soot leakage
  • Turbulent flames

Fingerprint Dive into the research topics of 'Damköhler number effects on soot formation and growth in turbulent nonpremixed flames'. Together they form a unique fingerprint.

  • Cite this