In Situ Measurement and Validation of Gaseous Species Concentrations of a Gas Turbine Model Combustor by Tunable Diode Laser Absorption Spectroscopy (TDLAS)

In the framework of a European research project, ONERA and DLR have studied the applicability of infrared laser techniques to gas turbine combustor measurements. The final goal is to replace gas analysis with probe measurements by optical techniques fulfilling the ICAO standards for engine emission measurements. Infrared laser absorption spectroscopy has the potential for fast, high spatial resolution measurements of combustion species with rugged equipment and therefore might contribute to the reduction of combustor development time and cost. Furthermore, the measurement of minor species in the combustor could help the understanding of the combustion process in the gas turbine. The tunable diode laser absorption technique of ONERA was used to probe CO, CO2, NO and H2O. The apparatus and measurement procedure including the upgrades for the combustor measurements are described. Successful measurements were achieved with CO inside and outside of the combustor. The reactive flow field of the model combustor was characterized with conventional measurement techniques. The CO measurements by TDLAS were compared with probe measurements that could be weighted by temperature and velocity measurements. Furthermore, temperature information was derived from the Laser measurements. The results are compared and further improvements are discussed.