COMBUSTOR-TURBINE AEROTHERMAL INTERACTION IN AN AXIAL TURBINE - INFLUENCE OF VARIED INFLOW CONDITIONS ON ENDWALL HEAT TRANSFER AND FILM COOLING EFFECTIVENESS

The Large Scale Turbine Rig (LSTR) at Technische Universit&Darmstadt, Germany is used to examine the aerothermal interaction of combustor exit flow conditions on the subsequent turbine stage. The rig resembles a high pressure turbine and is scaled to low Mach number conditions. A baseline configuration with axial, low-turbulent inflow and an aerodynamic inflow condition of a state-of-the-art lean combustor is modeled by the means of swirl generators, whose clocking position towards the nozzle guide vane's leading edge can be varied. A hub side coolant injection consisting of a double-row of cylindrical holes is implemented to examine the impact on endwall cooling. This paper is directed to study the effect of swirling inflow on heat transfer and film cooling effectiveness on the hub side end wall. Nusselt numbers are calculated using infrared thermography and the auxiliary wall method. This method allows for a high spatial resolution and in addition also yields adiabatic wall temperature data within the same measurement using a super-position approach. Aerodynamic measurements and numerical simulations complement the examination. The results for the baseline case show Nusselt numbers to increase significantly with higher coolant mass flux rates for the whole endwall area. With swirling inflow, in general, a decrease of film cooling effectiveness and an increase of Nusselt numbers is observed for identical mass flux rates in comparison to the baseline case. The difference varies depending on clocking position.