Characteristics of premixed flames stabilized in an axisymmetric curved-wall jet burner with tip modification

Daejoong Kim, Y. S. Gil, TaeWon Chung, Suk Ho Chung

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The stabilization characteristics of premixed flames in an axisymmetric curved-wall jet burner have been experimentally investigated. This burner utilized the Coanda effect on top of a burner tip. The initially spherical burner tip was modified to a flat tip and a concave tip in order to improve flame stabilization by providing enough space for flow recirculation above the burner tip region. The flow characteristics have been visualized using a schlieren technique. Small-scale turbulence structure has been observed mainly in the interaction jet region (located downstream of the recirculation region) for large jet velocity (Reynolds number >11,500). An appreciable amount of air entrainment was exhibited from the half-angle of the jet spread, approximately 20. The averaged planar laser-induced fluorescence images of the flames for this large velocity demonstrated that the strong signal of OH radicals, representing reaction zones, existed in the recirculation zone, while it was weak in the interaction jet region due to intermittency and local extinction by the generation of small scale turbulence. The OH radical signals strengthened again in the merged jet region (downstream of the interaction jet region). In extreme cases of Reynolds number over 19,000, a unique flame exhibiting OH radicals only in the recirculation zone was observed for the concave tip. The flame stabilization has been mapped by varying jet velocity and equivalence ratio, and the result showed that the stabilization characteristics were improved appreciably from the initial spherical tip design, especially for rich mixtures. The flow fields measured by a laser Doppler velocimetry confirmed the existence of recirculation zone and the expansion of the recirculation zones for the modified tips. The temperature profile measured by a coherent anti-Stokes Raman spectroscopy exhibited an intermittent nature, especially near the recirculation zone.
Original languageEnglish (US)
Pages (from-to)1397-1412
Number of pages16
JournalCombustion Science and Technology
Volume181
Issue number11
DOIs
StatePublished - Nov 10 2009

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: D. K. acknowledges the support by Sogang University Research Grant 200810026.

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • General Physics and Astronomy
  • General Chemical Engineering
  • General Chemistry
  • Fuel Technology

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