Theory and practice in using Fourier transform infrared spectroscopy to detect hydrocarbons in emissions from gas turbine engines

This paper describes the procedures used to detect hydrocarbons in emissions from gas turbine engines using non-intrusive Fourier Transform Infrared (FTIR) spectroscopy. The basic theory of FTIR is described together with the spectroscopic concepts necessary to be able to perform observations of hydrocarbons (HC). The processes of identification and quantification of the compounds present in combustion gases from infrared spectra are described and these techniques are applied to laboratory experiments using kerosene fuel burners. The results of field trials where exhausts from commercial aircraft were studied and unburnt hydrocarbons features in the C-H stretch region were measured are discussed. Quantitative measurements of HC were performed using the hexane equivalent concentration technique.