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Mid-infrared laser-induced thermal grating spectroscopy of hot water lines for flame thermometry

Hot, Dina LU ; Sahlberg, Anna Lena LU ; Aldén, Marcus LU and Li, Zhongshan LU (2020) In Proceedings of the Combustion Institute
Abstract

In this work we report the impact of using mid-infrared laser-induced thermal grating spectroscopy (IRLITGS) for temperature measurements in flames by probing hot water lines. The measurements have been performed in the product zone of laminar atmospheric CH 4 /H 2 /air flat flames with equivalence ratio ranging between 0.6 and 1.05. LITGS is a technique based on thermalization through collisions of the excited molecules for generation of a laser-induced grating, which then decays through thermal diffusion. As such, it tends to have limited application in atmospheric flames compared to flame measurements at elevated pressures due to the faster decay at low gas densities. However, by using mid-IR pump laser beams,... (More)

In this work we report the impact of using mid-infrared laser-induced thermal grating spectroscopy (IRLITGS) for temperature measurements in flames by probing hot water lines. The measurements have been performed in the product zone of laminar atmospheric CH 4 /H 2 /air flat flames with equivalence ratio ranging between 0.6 and 1.05. LITGS is a technique based on thermalization through collisions of the excited molecules for generation of a laser-induced grating, which then decays through thermal diffusion. As such, it tends to have limited application in atmospheric flames compared to flame measurements at elevated pressures due to the faster decay at low gas densities. However, by using mid-IR pump laser beams, it enables the generation of laser-induced gratings with large grating spacing, resulting in strong signal intensities and long signal durations. Single-shot IR-LITGS signals were recorded in the different CH 4 /H 2 /air flames that covered a temperature range between 1500 and 1800 K. To test the accuracy, the IR-LITGS flame temperature measurements were compared with laser Rayleigh scattering measurements and the result were in good agreement with each other. The IR-LITGS flame temperature measurements show a repetitive single-shot temperature precision better than 1% and an accuracy of 2.5% of the flame temperature. An IR-LITGS excitation scan of water in the flame shows that some ro-vibrational transitions exhibit no IR-LITGS signal, probably due to less efficient collisional energy transfer mechanism. This is important when deciding the wavelength to use for IR-LITGS flame temperature measurements using water absorption.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
Atmospheric flame, Laser-induced thermal grating spectroscopy, Mid-infrared, Temperature, Water
in
Proceedings of the Combustion Institute
publisher
Elsevier
external identifiers
  • scopus:85090474762
ISSN
1540-7489
DOI
10.1016/j.proci.2020.06.289
language
English
LU publication?
yes
id
82248025-ed1c-45d4-af2c-99aa7d41b682
date added to LUP
2020-10-02 11:49:20
date last changed
2020-10-03 01:59:52
@article{82248025-ed1c-45d4-af2c-99aa7d41b682,
  abstract     = {<p>In this work we report the impact of using mid-infrared laser-induced thermal grating spectroscopy (IRLITGS) for temperature measurements in flames by probing hot water lines. The measurements have been performed in the product zone of laminar atmospheric CH <sub>4</sub> /H <sub>2</sub> /air flat flames with equivalence ratio ranging between 0.6 and 1.05. LITGS is a technique based on thermalization through collisions of the excited molecules for generation of a laser-induced grating, which then decays through thermal diffusion. As such, it tends to have limited application in atmospheric flames compared to flame measurements at elevated pressures due to the faster decay at low gas densities. However, by using mid-IR pump laser beams, it enables the generation of laser-induced gratings with large grating spacing, resulting in strong signal intensities and long signal durations. Single-shot IR-LITGS signals were recorded in the different CH <sub>4</sub> /H <sub>2</sub> /air flames that covered a temperature range between 1500 and 1800 K. To test the accuracy, the IR-LITGS flame temperature measurements were compared with laser Rayleigh scattering measurements and the result were in good agreement with each other. The IR-LITGS flame temperature measurements show a repetitive single-shot temperature precision better than 1% and an accuracy of 2.5% of the flame temperature. An IR-LITGS excitation scan of water in the flame shows that some ro-vibrational transitions exhibit no IR-LITGS signal, probably due to less efficient collisional energy transfer mechanism. This is important when deciding the wavelength to use for IR-LITGS flame temperature measurements using water absorption.</p>},
  author       = {Hot, Dina and Sahlberg, Anna Lena and Aldén, Marcus and Li, Zhongshan},
  issn         = {1540-7489},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute},
  title        = {Mid-infrared laser-induced thermal grating spectroscopy of hot water lines for flame thermometry},
  url          = {http://dx.doi.org/10.1016/j.proci.2020.06.289},
  doi          = {10.1016/j.proci.2020.06.289},
  year         = {2020},
}