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

Journal Article · Tue Nov 01 00:00:00 EST 2005 · Applied Optics

DOI:https://doi.org/10.1364/AO.44.006701· OSTI ID:20702663

Liu, Jonathan T.C.; Rieker, Gregory B; Jeffries, Jay B; Gruber, Mark R; Carter, Campbell D; Mathur, Tarun; Hanson, Ronald K

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 {mu}m spectral region (2v1and v1+ v3overtone 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.

• OSTI ID: 20702663
• Journal Information: Applied Optics, Vol. 44, Issue 31; Other Information: DOI: 10.1364/AO.44.006701; (c) 2005 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6935
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
AIR
COMBUSTION
FEEDBACK
FIBERS
KHZ RANGE 01-100
MODULATION
NOISE
SEMICONDUCTOR LASERS
SIGNAL-TO-NOISE RATIO
SPECTROSCOPY
TEMPERATURE DISTRIBUTION
WATER
WATER VAPOR
WAVELENGTHS