An Approach to Detect Carbon Monoxide in Combustion Exhaust using Mid-Infrared Techniques

S. Pal, K. B. Ozanyan and H. McCann

School of Electrical & Electronic Engineering, University of Manchester, Manchester, UK, Email: Sandip.Pal@postgrad.manchester.ac.uk

ABSTRACT

Various groups have attempted single channel multi-pass or long path-length measurement of CO using mid-infrared (MIR) techniques. Single-pass short path-length measurement is being assessed in our work for tomographic measurement of the distribution of different minor species in the exhaust of combustion systems. We report here the spectroscopic study of CO in different absorption lines of strong fundamental bands in the mid-IR range. Criteria for the selection of light sources in this context are also reported.

Although strong spectral lines are available for CO in the mid-infrared region, strong water vapour and carbon dioxide interferences are also present. This work addresses the interference issues of major species present in the target combustion gas. The HITRAN 2004 database is used to predict the spectral lines of H2O and CO2 overlapping 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 Voigt profile is introduced to combine Doppler Broadening and Collisional Broadening to reflect both pressure and temperature effects. The percentages of absorption for different species and for different types of source are reported on the basis of computations. The optimum beam arrangement is discussed and a representative reconstruction with a three fan-beam arrangement is presented.

Keywords Spectroscopy, combustion, transimpedance, tomography, phantom.