M.Sc. Leon Schuhmann

Climate change and the increasing anthropogenic impact on the environment have made the optimization of industrial processes with respect to efficiency and pollutant emissions more important than ever. Achieving these goals requires a thorough understanding of the underlying physical processes. Gas turbines are of particular importance, as they play a key role in both power generation and aviation. Further improvements in their efficiency while simultaneously reducing emissions require detailed knowledge of the complex reactive gas phase inside the combustion chamber. However, the experimental characterization of the gas phase remains highly challenging. Harsh operating conditions, including high temperatures and pressures, together with the demanding requirements for measurement techniques in terms of robustness, process accessibility, minimal disturbance, accuracy, and high temporal and spatial resolution, preclude the use of many conventional diagnostic methods.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a robust, non-contact, and non-intrusive diagnostic technique for measuring temperature and species mole fractions in reactive gas phases. It enables highly accurate measurements with high temporal resolution, even under harsh operating conditions. However, because the measured absorption signal is integrated along the entire optical path, conventional TDLAS does not provide spatially resolved information about the measured quantities.

This limitation can be overcome by tomographic techniques, in which two-dimensional distributions are reconstructed from a large number of line-of-sight absorption measurements acquired along different beam paths. The combination of TDLAS and tomography therefore enables the spatially resolved determination of temperature and species mole fraction fields, providing a powerful tool for the characterization of complex reactive gas phases, such as those encountered in gas turbine combustion chambers. The development of corresponding measurement systems and reconstruction algorithms presents significant challenges from both theoretical and experimental perspectives.