Numerische und experimentelle Untersuchungen der Aerodynamik und Verbrennungsstabilität eines Vormischbrenners

Components of stationary gas turbines usually are replaced after long operation time to increase efficiency and power output of the engine and to reduce the emissions by use of latest technology. Lower flame peak temperatures for reduced emissions of nitrogen oxide can be achieved by an additional mixing length between the injection location and the flame. This work covers the improvement of aerodynamics of swirlers, the assessment of their flame flashback resistance and their robustness to installation conditions. Two different swirler concepts exhibiting an additional mixing length were studied. First a modification of the formerly used technology, which however did not perform successfully, and second a generic burner developed at the Lehrstuhl für Thermodynamik. The latter was adapted to the boundary conditions of a multi burner system. It showed in contrast to the generic burner poor flashback resistance in the combustion tests. The inflow conditions and the flow field inside the burner were studied to investigate the root cause. The study shows that the stability and robustness of the internal flow field of the burner have a major influence on the flashback limits. They do not only depend on thermodynamic properties and reacting processes. With these findings suggestions for the design of the flow field of premixed swirl burners with mixing tube can be formulated. Additionally a study of the aerodynamics and the cooling air injection of the developed burner in a multi burner system was performed. RANS models were calibrated with HSPIV-, HSLIF- and LES-single burner results by adapting the turbulent diffusivity. The study shows the flow field and cooling air distribution in the combustor. The quality of the mixture in the combustion chamber can provide information about possible regions of poor flame stabilization.