A spectroscopic study for detection of carbon- monoxide using mid-infrared techniques for single- pass measurement

Tomographic imaging of minor species in combustion exhaust is an important requirement for combustion engineering. Only one group has tried carbon monoxide imaging in laminar flames in the mid-infrared region. A number of attempts have been made by different groups for single-channel multi-pass or long path-length measurement of CO. Singlepass measurement is being assessed in our work for tomographic measurement of the distribution of minor species. We report here the spectroscopic study of CO in different absorption lines of the strong fundamental bands in the mid-IR range. The criteria for selection of a light source in this context are also considered. Although strong spectral lines are available for CO in the mid-infrared region, strong water vapour and carbon dioxide interferences are also present. This addresses the choice of such useful spectral lines under interference by major species. The HITRAN 2004 database is used to predict the spectral lines of H2O and CO2 near the fundamental spectrum of CO in the mid-IR range. The exhaust condition in respect of temperature and pressure is considered in order to study the broadening of the spectral lines. The percentages of absorption for different species for different types of light sources are reported on the basis of computations. The concept can be readily extended to further species of interest in the presence of other interfering species. Different laser sources and spectroscopic methods are considered to design a strategy suitable to this application.