The trailing edge base pressure is known to play a significant role in the profile losses of turbine blades in particular at transonic outlet Mach numbers. Recent tests have shown that the assumption of an isobaric near wake region is wrong because of the highly unsteady character of the near wake flow which affects directly the trailing edge base pressure. New experimental data show the evolution of the trailing edge base pressure in function of the downstream Mach number from a uniform base pressure at moderate subsonic Mach numbers to an increasingly strong non-uniform distribution up into the transonic range followed by a sudden return to an isobaric base trailing edge pressure. To get more insight into the unsteady flow features, numerical simulations are carried out. A LES approach is validated and employed in this work to analyze three different operating conditions for the profile, representing three configurations of the flow and the trailing edge shock system.

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The aim of the present paper is to analyze and discuss in detail the effects of the upstream incoming wakes on both the aerodynamic loading and the evolution of the laminar separation bubble developing along the suction side of the high-lift T106-C low pressure turbine blade at engine similar Reynolds and Mach numbers, but at a low free stream turbulence level. The investigation is carried out numerically by means of steady and unsteady RANS simulations for two different Reynolds numbers (100,000 and 140,000), employing the SST turbulence model coupled to the γ–Re~θt transition model. The numerical results are compared with the experimental data provided by the von Karman Institute in terms of variation of losses and blade loading between steady and unsteady inflow conditions. In general, the incoming wakes have a crucial effect both on the reduction of the separation bubble and on the modification of the blade loading. This is analyzed in detail, in order to separate these contributions.

Modern Lean Burn combustors generate a complex field at the High Pressure turbine (HPT) inlet, characterized by non-uniform velocity and temperature distributions, together with very high turbulence levels (up to 25%). For these extreme conditions, classical numerical methods employed for the HPT design, such as Reynolds Averaged Navier Stokes (RANS) simulation, suffer from a lack of validation. This leads to a reduced confidence in predicting the combustor-turbine interactions, which requires to use extra safety margins, to the detriment of the overall engine performance. Within the European FACTOR project, a 360° non reactive combustor simulator and a 1.5 HPT stage are designed to get more insight into the mutual interaction of these two components. A first experimental and numerical campaign has demonstrated the potential of Large Eddy Simulations (LES) to accurately reproduce the turbulent flow field development at the combustor outlet. The aim of the present paper is to exploit the accuracy of LES to validate less time-consuming RANS models in predicting the hot streak migration in the turbine stage. In this sense, LES results are used as a reference to discriminate the different RANS simulations in terms of turbulence modeling and aerothermal predictions. The current investigations clearly indicate that turbulence and hot streak diffusion within the HPT are strongly linked. In this sense, the choice of the RANS turbulence model and the inlet turbulent conditions plays a major role in modeling the thermal behavior for the stator and rotor blades.