Aerothermal Investigation of the Flow around an Airfoil with Endwall Cooling Air Injection

Lean combustion processes evolve in greater extent both in stationary gas turbines and in propulsion systems due to the need for rising fuel efficiency. However, lean combustion processes also result in higher overall temperatures and steeper temperature gradients in near-endwall regions of the gas turbines. In order to ensure longer life cycles of the components the injection of cooling air is seen as one means to reduce strains induced by temperature. At the Technical University Darmstadt a generic test rig is assembled and used to investigate the aerodynamic and thermal interaction of cooling air injection and a primary air flow in front of an airfoil profile inside a flow channel. Steady-state measurements of heat fluxes within the endwall and derived entities such as adiabatic heat transfer coefficients and convective cooling effectiveness are used to assess the quality of cooling effects for varied flow rates of injected cooling air. The examinations of both steady-state and instantaneous aerodynamic measurements with the help of particle image velocimetry (PIV) show a statistical interdependency of known aerodynamic phenomena with the resulting heat transfer into the endwall.