Tunable diode laser spectroscopy with wavelength modulation: calibration-free measurements of gas compositions at elevated temperatures and varying pressure

A.J. McGettrick, W. Johnstone, J.D. Black

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18 Citations (Scopus)

Abstract

The validity of two new approaches to tunable diode laser spectroscopy (TDLS) in the near-IR, namely the residual amplitude modulation approach and the phasor decomposition method, is investigated for application in industrial process monitoring where the operating temperatures and pressures are high and subject to significant change. Both techniques allow the recovery of absolute absorption profile line shapes and are completely calibration free, making them very attractive for online deployment in stand alone instrumentation in harsh environments where the calibration factors in conventional TDLS methods are subject to significant cumulative errors and drift. Currently established TDLS techniques, and indeed conventional gas composition analysis techniques, suffer from significant limitations when applied under these conditions, and there is a clear need for the development of a suitable alternative. The primary focus in this work is the analysis of water vapor in solid oxide fuel cell diagnostics where the operating temperatures range from 700 degrees C to 950 degrees C, the gas pressures are subject to change and the recovered signal levels are low. The 1391.7 nm overtone water vapor transition is interrogated over the above temperature range of interest at concentrations of 6%-50%, while the 1650.96 nm methane transition is also analyzed over a range of gas pressures at a fixed concentration of 1%. Excellent agreement between the experimentally recovered absorption line shapes and simulations based on parameters from the HITRAN (2004) database is observed; further evidence for the efficacy of the techniques is demonstrated through the accuracy of the gas concentration measurements which were achieved by curve-fitting absorption line shape simulations to the experimental data.
LanguageEnglish
Pages3150-3161
Number of pages12
JournalJournal of Lightwave Technology
Volume27
Issue number15
DOIs
Publication statusPublished - 1 Aug 2009

Fingerprint

gas composition
laser spectroscopy
line shape
diodes
operating temperature
modulation
gas pressure
water vapor
wavelengths
curve fitting
solid oxide fuel cells
temperature
methane
simulation
recovery
harmonics
decomposition
profiles
gases

Keywords

  • absolute line shape recovery
  • calibration free
  • industrial process monitoring
  • solid oxide fuel cells (SOFC)
  • tunable diode laser spectroscopy (TDLS)
  • wavelength modulation
  • spectroscopy

Cite this

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title = "Tunable diode laser spectroscopy with wavelength modulation: calibration-free measurements of gas compositions at elevated temperatures and varying pressure",
abstract = "The validity of two new approaches to tunable diode laser spectroscopy (TDLS) in the near-IR, namely the residual amplitude modulation approach and the phasor decomposition method, is investigated for application in industrial process monitoring where the operating temperatures and pressures are high and subject to significant change. Both techniques allow the recovery of absolute absorption profile line shapes and are completely calibration free, making them very attractive for online deployment in stand alone instrumentation in harsh environments where the calibration factors in conventional TDLS methods are subject to significant cumulative errors and drift. Currently established TDLS techniques, and indeed conventional gas composition analysis techniques, suffer from significant limitations when applied under these conditions, and there is a clear need for the development of a suitable alternative. The primary focus in this work is the analysis of water vapor in solid oxide fuel cell diagnostics where the operating temperatures range from 700 degrees C to 950 degrees C, the gas pressures are subject to change and the recovered signal levels are low. The 1391.7 nm overtone water vapor transition is interrogated over the above temperature range of interest at concentrations of 6{\%}-50{\%}, while the 1650.96 nm methane transition is also analyzed over a range of gas pressures at a fixed concentration of 1{\%}. Excellent agreement between the experimentally recovered absorption line shapes and simulations based on parameters from the HITRAN (2004) database is observed; further evidence for the efficacy of the techniques is demonstrated through the accuracy of the gas concentration measurements which were achieved by curve-fitting absorption line shape simulations to the experimental data.",
keywords = "absolute line shape recovery, calibration free, industrial process monitoring, solid oxide fuel cells (SOFC), tunable diode laser spectroscopy (TDLS), wavelength modulation, spectroscopy",
author = "A.J. McGettrick and W. Johnstone and J.D. Black",
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T2 - Journal of Lightwave Technology

AU - McGettrick, A.J.

AU - Johnstone, W.

AU - Black, J.D.

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N2 - The validity of two new approaches to tunable diode laser spectroscopy (TDLS) in the near-IR, namely the residual amplitude modulation approach and the phasor decomposition method, is investigated for application in industrial process monitoring where the operating temperatures and pressures are high and subject to significant change. Both techniques allow the recovery of absolute absorption profile line shapes and are completely calibration free, making them very attractive for online deployment in stand alone instrumentation in harsh environments where the calibration factors in conventional TDLS methods are subject to significant cumulative errors and drift. Currently established TDLS techniques, and indeed conventional gas composition analysis techniques, suffer from significant limitations when applied under these conditions, and there is a clear need for the development of a suitable alternative. The primary focus in this work is the analysis of water vapor in solid oxide fuel cell diagnostics where the operating temperatures range from 700 degrees C to 950 degrees C, the gas pressures are subject to change and the recovered signal levels are low. The 1391.7 nm overtone water vapor transition is interrogated over the above temperature range of interest at concentrations of 6%-50%, while the 1650.96 nm methane transition is also analyzed over a range of gas pressures at a fixed concentration of 1%. Excellent agreement between the experimentally recovered absorption line shapes and simulations based on parameters from the HITRAN (2004) database is observed; further evidence for the efficacy of the techniques is demonstrated through the accuracy of the gas concentration measurements which were achieved by curve-fitting absorption line shape simulations to the experimental data.

AB - The validity of two new approaches to tunable diode laser spectroscopy (TDLS) in the near-IR, namely the residual amplitude modulation approach and the phasor decomposition method, is investigated for application in industrial process monitoring where the operating temperatures and pressures are high and subject to significant change. Both techniques allow the recovery of absolute absorption profile line shapes and are completely calibration free, making them very attractive for online deployment in stand alone instrumentation in harsh environments where the calibration factors in conventional TDLS methods are subject to significant cumulative errors and drift. Currently established TDLS techniques, and indeed conventional gas composition analysis techniques, suffer from significant limitations when applied under these conditions, and there is a clear need for the development of a suitable alternative. The primary focus in this work is the analysis of water vapor in solid oxide fuel cell diagnostics where the operating temperatures range from 700 degrees C to 950 degrees C, the gas pressures are subject to change and the recovered signal levels are low. The 1391.7 nm overtone water vapor transition is interrogated over the above temperature range of interest at concentrations of 6%-50%, while the 1650.96 nm methane transition is also analyzed over a range of gas pressures at a fixed concentration of 1%. Excellent agreement between the experimentally recovered absorption line shapes and simulations based on parameters from the HITRAN (2004) database is observed; further evidence for the efficacy of the techniques is demonstrated through the accuracy of the gas concentration measurements which were achieved by curve-fitting absorption line shape simulations to the experimental data.

KW - absolute line shape recovery

KW - calibration free

KW - industrial process monitoring

KW - solid oxide fuel cells (SOFC)

KW - tunable diode laser spectroscopy (TDLS)

KW - wavelength modulation

KW - spectroscopy

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