Hyperacceleration effects on turbulent combustion in premixed step-stabilized flames

Andrew P. Lapsa, Werner J.A. Dahm

Research output: Contribution to journalConference articlepeer-review

24 Scopus citations

Abstract

Experimental results are presented from an investigation of the effects of large transverse accelerations on flame propagation and blowout limits in premixed step-stabilized flames. The accelerations, which exceed ±10,000 g in the present study, induce large body forces on the high-density reactants and low-density products. These body forces can substantially alter the flame propagation mechanisms and dramatically increase the flame blowout limits. Sustained centripetal accelerations ac = U2/R are created by flowing a premixed propane-air reactant stream with equivalence ratios 0.7 ≤ Φ ≤ 1.9 at various speeds U through a semicircular channel with radius R. A backward-facing step of height h on the radially outer (a c > 0) or inner (ac < 0) wall stabilizes the flame. For ac > 0 the acceleration acts to force high-density reactants into the recirculation zone and low-density products into the reactant stream, while ac < 0 forces hot products into the recirculation zone and impedes cold reactants from entering this zone. An otherwise identical straight channel provides corresponding baseline (ac = 0) results for comparison. The flow speed U, equivalence ratio Φ, and step height h are systematically varied for ac = 0, ac > 0, and a c < 0. Shadowgraph and chemiluminescence imaging show that as ac → +∞ the propagation of the flame across the channel becomes independent of the flame burning velocity and instead is primarily due to large-scale "centrifugal pumping" driven by the induced body forces. For ac →-∞ the body forces effectively segregate reactants and products to produce a nearly flat flame. In both cases, for large |ac| values the resulting blowout limits can be substantially higher than those at ac = 0.

Original languageEnglish (US)
Pages (from-to)1731-1738
Number of pages8
JournalProceedings of the Combustion Institute
Volume32 II
DOIs
StatePublished - Mar 16 2009
Externally publishedYes
Event32nd International Symposium on Combustion - Montreal, QC, Canada
Duration: Aug 3 2008Aug 8 2008

Keywords

  • Blowout limits
  • Flame propagation
  • Flame stability
  • Premixed combustion
  • Step-stabilized flames

ASJC Scopus subject areas

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

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