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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Editor: Glenn D. Boreman
  • Vol. 44, Iss. 31 — Nov. 1, 2005
  • pp: 6701–6711

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor

Jonathan T. C. Liu, Gregory B. Rieker, Jay B. Jeffries, Mark R. Gruber, Campbell D. Carter, Tarun Mathur, and Ronald K. Hanson  »View Author Affiliations


Applied Optics, Vol. 44, Issue 31, pp. 6701-6711 (2005)
http://dx.doi.org/10.1364/AO.44.006701


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Abstract

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34–1.47 μm spectral region (2v1 and v1 + v3 overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy in such situations.

© 2005 Optical Society of America

OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.1740) Instrumentation, measurement, and metrology : Combustion diagnostics
(300.0300) Spectroscopy : Spectroscopy
(300.1030) Spectroscopy : Absorption
(300.6260) Spectroscopy : Spectroscopy, diode lasers
(300.6380) Spectroscopy : Spectroscopy, modulation

Citation
Jonathan T. C. Liu, Gregory B. Rieker, Jay B. Jeffries, Mark R. Gruber, Campbell D. Carter, Tarun Mathur, and Ronald K. Hanson, "Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor," Appl. Opt. 44, 6701-6711 (2005)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-44-31-6701

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