Obtaining and Interpreting Near-Infrared Wavelength Modulation Absorption Signals From Hot Fire Gases: Practical Issues.
Obtaining and Interpreting Near-Infrared Wavelength
Modulation Absorption Signals From Hot Fire Gases:
Blevins, L. G.; Peterson, B. W.
Chemical and Physical Processes of Combustion, Fall
Technical Meeting. Proceedings. Combustion
Institute/Eastern States Section. October 13-19, 1999,
Raleigh, NC, 85-88 pp, 1999.
carbon monoxide; fiber optics; fire measurements;
infrared spectroscopy; instrument design; lasers
Near-infrared tunable diode laser absorption
spectroscopy (TDLAS) shows promise for measuring
concentrations of several gaseous species important in
fires, including CH4, 02, C2H2, C2H4, CO, CO2 and H2O.
Researchers at NIST are presently studying the possible
application of near-infrared TDLAS for rapid measurement
of CO concentration in and around fires. Near-infrared
diodes are compact, spectrally narrow, and rapidly
tunable, and the potential exists to deliver diode light
into and out of real-scale fires using rugged and
readily-available silica fiber optics. The goal of the
NIST project is to develop a diode laser sensor capable
of measuring CO concentration at temperatures between
300 K and 1200 K in fire gases partially obscured by
soot. This abstract describes some practical signal
interpretation issues found to be important during
sensor development. Previous studies on the use of
near-infrared diodes for CO measurement have focused on
determining CO amounts in room-temperature absorption
cells with controlled gas composition. Some recent
studies of CO in combustion gases employed rapid probe
sampling with a multi-pass cell/diode laser arrangement,
and an in situ measurement of CO concentration in the
hot exhaust of a premixed methane/air flame was recently
reported. Near-infrared TDLAS has been used in fire
research to quantify hydrogen fluoride concentration in
post-flame gases following fire suppression.