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Mid-infrared PS and LIF detection of CH4 and C2H 6 in cold flows and flames at atmospheric pressure

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Author

Summary, in English

Mid-infrared polarization spectroscopy (IRPS) and laser-induced fluorescence (IRLIF) have been applied for detection of methane and ethane in atmospheric pressure cold flows and flames. Lines belonging to the asymmetric C-H stretching vibration bands v<sub>3</sub> and v<sub>7</sub> for methane and ethane, respectively, were probed with a tunable infrared laser beam at about 3.4 μm, which was obtained from difference frequency generation in a LiNbO<sub>3</sub> crystal pumped by a dye-laser beam and a Nd:YAG fundamental laser beam. The dependence of IRPS and IRLIF signal of CH<sub>4</sub> on different buffer gases, including He, Ar, N<sub>2</sub>, and CO<sub>2</sub> was investigated. Simultaneous measurements of IRPS and IRLIF signals allowed a direct comparison of the two techniques, and IRPS was found to be superior in detection sensitivity and background discrimination. IRPS excitation scans of a methane and ethane mixture diluted in Ar were also performed in a jet at ambient pressure and temperature. Lines in the spectrum belonging to methane and ethane were fully recognized and assigned. From the ethane lines in the IRPS excitation spectrum, a detection limit of 50 ppm was conservatively estimated, and this indicates that IRPS is a promising sensitive technique for hydrocarbon identification and detection. Finally, CH<sub>4</sub> IRPS detection in a CH<sub>4</sub>/H<sub>2</sub>/air premixed flat flame was demonstrated, with spatially resolved IRPS CH<sub>4</sub> measurements along different heights in the flame.

Department/s

Publishing year

2005

Language

English

Pages

1629-1636

Publication/Series

Proceedings of the Combustion Institute

Volume

30

Issue

1

Document type

Journal article

Publisher

Elsevier

Topic

  • Atom and Molecular Physics and Optics

Keywords

  • Infrared polarization spectroscopy (IRPS)
  • Laser-induced fluorescence
  • Excitation spectrum
  • Laser combustion diagnostics

Status

Published

ISBN/ISSN/Other

  • ISSN: 1540-7489