Experimental investigations of flame-cooling air interaction in an effusion cooled pressurized single sector model gas turbine combustor

Abstract

Within this thesis, the mutual interaction between the flame and cooling air within an effusion cooled single sector model gas turbine combustor is investigated at elevated pressure. \nAlthough effusion cooling has been widely studied in the last decades with respect to heat transfer and total film cooling effectiveness, fundamental aspects of the interaction mechanisms with the reacting main flow are not yet well understood. \n \nTypically, experimental investigations are conducted either by reducing the complexity by placing an effusion cooling plate in a test section downstream of a hot gas source, which allows a good experimental accessibility and well controlled boundary conditions, or by reducing the complexity on the diagnostics side, e.g. by using sampling probe measurements at the exhaust of a close-to-reality test rig. \nThe first approach does not facilitate investigations of the interaction mechanisms between the reacting main flow and effusion cooling air, as they are spatially separated. \nThe second approach on the other hand includes all mechanisms, but measurements are not conducted spatially resolved within the test section. \nWithin this work, an effusion cooling plate is mounted within a generic test rig which features a swirl-stabilized turbulent flame at elevated inlet temperature and pressure to fully capture the influence of unsteady heat release, convection, radiation and chemical reactions in the vicinity of the liner. \n \nQuantitative and semi-quantitative advanced laser diagnostics with high temporal and spatial resolution are employed to identify sensitivities of flame-cooling air interaction with respect to important boundary conditions that affect the flow and temperature field and cooling performance. \nMixing between the reacting main flow and effusion cooling air is investigated by a combination of quantitative planar laser-induced fluorescence of the hydroxyl radical (OH) and nitric oxide, seeded to the effusion cooling air. \nThis data allows to identify the relative occurrence of mixing processes before, during and after reaction. \nFurthermore, measurements of the thermochemical state, as represented by the carbon monoxide (CO) mole fraction and the gas phase temperature, were conducted using combined quantitative CO laser induced fluorescence (LIF) and ro-vibrational coherent anti-Stokes Raman spectroscopy with nitrogen as a resonant species. \nSimultaneous LIF measurements of OH, CO and formaldehyde (CH2O) were executed to investigate the sensitivity of CO production and oxidation near reaction zones to the boundary conditions. \n \nThe acquired data shows that interaction processes between the flame and cooling air locally influence the structure of the premixed flame across the preheating zone, main reaction zone and the exhaust. \nSpatially, these interaction processes are not limited to the area close to the effusion cooled liner but extend into the primary zone by recirculation.