Hot Streak Migration in a Turbine Stage: Integrated Design to Improve Aero-Thermal Performance

Hot streaks can cause localized hot spots on the blade surfaces in a high-pressure turbine, increasing the heat load locally and even leading to material loss in regions such as the rotor blade tip. This study explores numerically the effect of the hot streak's orientation at the stator inlet on the rotor blade heat load and on the tip in particular. The inlet boundary conditions are taken from the hot streak experiment conducted in the axial turbine facility “LISA” at ETH Zurich. Using a particle tracking tool in conjunction with time-resolved simulations a detailed analysis of the migration pattern of the hot streak is performed and the underlying mechanisms are discussed. The effect of clocking the hot streak from mid-pitch to the stator pressure side and in the opposite direction is examined. By clocking this particular hot streak even 10% of the stator pitch towards the pressure side up to 24 K reduction in the rotor blade tip adiabatic wall temperatures is achieved. The validity of the particle migration pattern is also tested on an elliptical hot streak shape. Changing the orientation of the hot streak at the inlet plane a heat load re-distribution parallel to the migration characteristics is observed. Finally, based on the observations made, the implications for an integrated combustor-turbine design strategy are discussed.