Development of improved PLIF CH detection using an Alexandrite laser for single-shot investigation of turbulent and lean flames

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Abstract

We report on the development of planar laser-induced fluorescence (PLIF) for CH imaging with improved detection sensitivity for single-shot investigations of turbulent, lean, premixed flames. A ringcavity, pulsed Alexandrite laser was frequency-doubled to excite the lines in the R-branch band-head of the B-X (0,0) band and broadband fluorescence from the B-X (0,1), A-X (1,1) and (0,0) bands, overlapping in the spectral range around 431 nm, was collected. The employed Alexandrite laser, which is characterized by its long pulse duration (150 ns), gives a tunable laser beam around 775 nm with a pulse energy for the second harmonic at the CH absorption wavelength of about 70 mJ. Moreover, the laser has the possibility to be operated in narrow bandwidth (100 MHz) or broad bandwidth (8 cm<sup>-1</sup>). An introductory high resolution excitation scan over the R-branch band-head was performed and, in addition, saturated excitation with the broadband option of the laser was investigated. By simultaneous excitation of several rotational transitions and to bring these transitions close to saturation, high signal-to-noise ratios were reached over a wide range of equivalence ratios. A sharp and thin CH layer was observed in single-shot PLIF images from laminar premixed methane/air flames from Φ = 0.6 to Φ = 1.5. Finally, the impact of the developed CH PLIF technique is demonstrated in a highly turbulent, lean, partially premixed methane/air flame established on a co-axial jet flame burner. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Fluid Mechanics and Acoustics
  • Atom and Molecular Physics and Optics

Keywords

  • Lean premixed methane/air flame, Planar laser-induced fluorescence, CH radical, Laser combustion diagnostics, Turbulent combustion
Original languageEnglish
Title of host publicationProceedings of the Combustion Institute
PublisherElsevier
Pages727-735
Volume31 I
Publication statusPublished - 2007
Publication categoryResearch
Peer-reviewedYes
Event31st International Symposium on Combustion - Heidelberg, Germany
Duration: 2006 Aug 52006 Aug 11

Publication series

Name
Volume31 I
ISSN (Print)1873-2704
ISSN (Electronic)1540-7489

Conference

Conference31st International Symposium on Combustion
CountryGermany
CityHeidelberg
Period2006/08/052006/08/11