Optical Tomography in Combustion

The new methodology of optical infrared tomography of flames and hot gas flows was developed in the PhD project with a view to future industrial applications. In particular, the methodology for the tomographic reconstruction of an axisymmetric lab flame temperature profile was developed and tested in the lab using Fourier transform infrared spectroscopy techniques, including a new tomographic measurement scheme, sweeping scanning, having great potential for industrial applications with limited optical access.

The results were compared to the reference point measurements on the same flame and the deviations are discussed. The methods are shown to have promising potential for future industrial applications. The new multichannel infrared spectrometer system as a first prototype of the infrared spectroscopic tomography system was developed in the PhD project for simultaneous fast transient infrared spectral measurements at several line-of-sights with a view to applications for tomographic measurements on full-scale industrial combustion systems.

The system was successfully applied on industrial scale for simultaneous fast exhaust gas temperature measurements in the three optical ports of the exhaust duct of the large Diesel engine. The results were compared to the measurements performed by another system employing spectral properties of nitric oxides in the ultraviolet range.

A good agreement was observed between the results obtained using the two different systems. In the context of the PhD project, it was also important to investigate the spectral properties of major combustion species such as carbon dioxide and carbon monoxide in the infrared range at high temperatures to provide the theoretical background for the development of the optical tomography methods.

The new software was developed for the line-by-line calculations of the transmission spectra of a carbon dioxide/carbon monoxide mixture which is able to use within reasonable time the most recent but huge CDSD-4000 database containing updated high-temperature spectroscopic line-by-line data. The software was used for the line-by-line calculations of the transmission spectra of the carbon dioxide/carbon monoxide mixture at high temperatures and the results were compared to the measurements in the high-temperature flow gas cell carried out before the PhD project.

The results and discussion are presented in a journal article [Evseev et al. JQSRT 113 (2012) 2222, 10.1016/j.jqsrt.2012.07.015] included in the PhD thesis as an attachment. The knowledge and experience gained in the PhD project is the first important step towards introducing the advanced optical tomography methods of combustion diagnostics developed in the project to future industrial applications.