A Tunable Diode Laser Gas-Density Spectrometry with the Coverage from Trace Species to Rich Fuel Transients

概要

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An atmospheric trace gas monitor with a PbSnTe laser has been developed. The open, 1 m optical path in a single-folded configuration enables local and non-contact measurement in a portable apparatus. The accuracy depends on optical noise, and a technique in diode-current modulation was effective in suppressing it. Analysis of the system noise based on the experimental data was made and a 10 ms interval was sufficient to attain an accuracy 3 ppm for methane. Field measurements were made and a rapid fluctuation in the atmospheric methane density was recorded. Further, with the principle of this monitor, the non-contacting and temporally continuous measurement was made for radius of spherical flame front on the progress of a single combustion. Abundance of unburned spectrum at a time instant was obtained with using a chirping diode laser beam passing through the spherical vessel. Experimental results are compared with those calculated only from the pressure with using a theory of Lewis and von-Elbe as well as those obtained with ion probes. Results of three methods agree well when the initial pressure is low but do not at high pressure. This method has the advantage of the accuracy at the initial stage.
福山大学の論文