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

McGettrick, A.J. and Johnstone, W. and Cunningham, R. and Black, J.D. (2009) Tunable diode laser spectroscopy with wavelength modulation : calibration-free measurements of gas compositions at elevated temperatures and varying pressure. Journal of Lightwave Technology, 27 (15). pp. 3150-3161. ISSN 0733-8724

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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.

Item type: Article
ID code: 14761
Keywords: absolute line shape recovery, calibration free, industrial process monitoring, solid oxide fuel cells (SOFC), tunable diode laser spectroscopy (TDLS), wavelength modulation, spectroscopy, Electrical engineering. Electronics Nuclear engineering, Physics, Atomic and Molecular Physics, and Optics
Subjects: Technology > Electrical engineering. Electronics Nuclear engineering
Science > Physics
Department: Faculty of Engineering > Electronic and Electrical Engineering
Faculty of Science > Strathclyde Institute of Pharmacy and Biomedical Sciences
Related URLs:
    Depositing user: Strathprints Administrator
    Date Deposited: 16 Jun 2010 14:55
    Last modified: 04 Sep 2014 23:58
    URI: http://strathprints.strath.ac.uk/id/eprint/14761

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