Oscillatory extinction of spherical diffusion flames: Micro-buoyancy experiment and computation

S. W. Yoo, E. W. Christiansen, C. K. Law

Research output: Contribution to journalConference article

11 Scopus citations

Abstract

The transient extinction behavior of near-limit spherical diffusion flames under microbuoyancy conditions was experimentally investigated. An inverse flame configuration was employed with the oxidizer being ejected from a porous sphere burner into a fuel (H2) environment in a low-pressure (0.096 atm) chamber to effectively minimize buoyancy. Various inert gasses (N2, CO2, and He) were used to dilute the oxidizer to change the Lewis number and radiative properties of the mixture so that both the transport-induced and the radiative-induced limit could be achieved. Extinction was triggered by gradually decreasing the H2 mole fraction in the ambient. At the transport-induced limit, extinction is characterized by sudden quenching of the flame as demonstrated by a rapid decrease of the radiometer signal voltage. However at the radiation-induced limit extinction is preceded by oscillations in the flame luminosity that grows in amplitude before extinction. Computational simulation of the experiment was performed by using a one-dimensional spherically symmetric domain with detailed chemistry and transport and radiatively thin heat loss. Oscillations were computationally observed at the radiative limit with approximately the same frequency as the experiment (∼2 Hz). However, the critical ambient H2 mole fraction that triggered oscillation was much larger in the simulation than in the experiment, possibly due to the neglect of radiation reab-sorption in the simulation.

Original languageEnglish (US)
Pages (from-to)29-36
Number of pages8
JournalProceedings of the Combustion Institute
Volume29
Issue number1
DOIs
StatePublished - Jan 1 2002
Event30th International Symposium on Combustion - Chicago, IL, United States
Duration: Jul 25 2004Jul 30 2004

All Science Journal Classification (ASJC) codes

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

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