- Author
-
Shaddix, C.
- Title
- Species Measurements With Near-IR Tunable Diode Lasers in Demanding Environments (Including Fires). BFRL Fire Research Seminar.
Seminar. VHS Video.
- Coporate
- Sandia National Labs., Livermore, CA
- Report
-
Video
December 15, 1997
- Keywords
-
lasers
|
fiber optics
- Abstract
- We have recently applied tunable diode laser spectroscopy to perform in situ measurements in a pilot-scale rotary kiln incierator and in a sealed tunnel chamer in which artillery shell detonations and rocket motor burns occurred. For these environments, the use of near-IR TDLs is advantageous for remote operation and coupling into low-cost communication-grade fiber-optics. High-frequency wavelength modulation of the diodes and second harmonic (2f) detection are used to improve measurement sensitivity for the near-IR molecular overtone transitions. In the incinerator tests, TDL measurements were also performed in an extractive probe/long-path cell arrangement and allowed direct comparison of calibrated CO and CH4 signals to standard NDIR and FID gas analyzer measurements. In situ measurements have proven to be challenging in these environments due to weakened linestrengths at high temperatures, the presence of interfering hot-band CO2 and H2O lines, and highly variable extents of laser attenuation from particulates in the smpled flow (soot in the case of incierator, and concrete dust in the case of the artillery shell detonations). These same difficulties will be encountered in a new project developing a TDL technique for simultaneous quantification of chemical species and soot in large-scale pool fires. Species of interest for this investigation include combustion products, fuel pyrolysis species, and combustion intermediates: CO2, H2O, CH4, CO, and perhaps C2H2, C2H4, or O2. The approach we are taking in developing the TDL technique for this purpose will be discussed.