Abstract
A diode-laser sensor system, comprised of a tunable external-cavity diode laser (ECDL) operating near 2.0 μm and fiber-optic components, has been developed to measure the gas temperature and the concentrations of CO2 and H2O in the combustion and exhaust regions of a flat-flame burner (C2H4/air) using absorption spectroscopy techniques. The present system extends the techniques developed previously 1-4 for the measurement of H2O and CO2 by probing relatively stronger vibrational bands and thus offers higher measurement sensitivity. Measurements of individual transitions (1-cm−1 scans) were recorded by adjusting the internal grating to particular center wavelengths and by applying a 6-volt sawtooth voltage waveform at a 1.25-Hz repetition rate to the wavelength modulation input. Temperature may be determined either from the ratio of measured H2O (ν1+ ν2, ν2 + ν3 bands) or CO2 (ν1+2ν2+ ν3 band) absorbances. Species (H2O, CO2) concentrations were determined from the measured temperature and absorbances of appropriate transitions recorded by tuning the ECDL wavelength across selected transitions within the 250 cm−1 laser tuning range centered at 2.02 μm.
© 1998 Optical Society of America
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