Investigation of High Pressure Turbine End-Wall Film Cooling Performances under Realistic Inlet Conditions
The mean value of turbine entry temperature increased to improve efficiency and specific power. Due to the combustor characteristics, thermal and aero-dynamics non-uniformities can be individuated at the turbine inlet section. Then, a further increase in the inlet temperature will generate in the next years harmful conditions also for vane end-walls. In other words, it is necessary to use realistic turbine inlet temperature and velocity profiles to evaluate the effects generated by this design tendency. The objective of the present work is to analyze a cooled high-pressure vane in terms of adiabatic effectiveness and aerodynamic behavior. An end-wall cooling geometry with both fan-shaped and cylindrical holes, tested by EPFL in the frame of the EU funded TATEF2 project, has been chosen. Numerical analysis has been performed by the Energy Engineering Department of the University of Florence. Inlet non-uniformity of total temperature and velocity profile has been considered as representative of realistic situations. According to the distributions of Cd, BR and ηaw, a steady RANS simulation is able to reproduce the experimental data with an error slightly higher that the one of the measurements. Once the inlet T0 profile is imposed, an increase of 100% in the laterally averaged ηaw, generated by the radial T0 distribution can be achieved. The improved performance is visible on the 2D maps, too. The gain in cooling efficiency is limited by the inlet swirl, whose presence modifies the horseshoe vortex development and generates a stronger passage vortex with a detrimental effect for the platform cooling. Therefore, an accurate estimation of the inlet conditions is vital for machine reliability.