58816 - High-Fidelity Simulations of a High-Pressure Turbine Vane With End Walls: Impact of Secondary Structures and Spanwise Temperature Profiles on Losses 

High-pressure turbines (HPT) remain challenging to simulate as they typically experience extreme working conditions including high temperature, high Reynolds and Mach numbers, and high levels of unsteadiness and turbulence. Moreover, the uncertainty of the temperature distribution and turbulence fluctuations coming from the combustor exit significantly affects the prediction of the thermodynamic behavior of the flow. In the present study, highly resolved large-eddy simulations (LES) of a VKI LS-89 HPT blade (T. Arts et al., 1990) with spanwise end-walls are performed at a Reynolds number of 0.57 million and an exit Mach number of 0.9. Moreover, turbulence fluctuations, with amplitudes up to 20% of the inlet mean velocity and length scales up to 20% of the axial chord, are introduced at the inflow to simulate the large-scale high-amplitude unsteadiness from the combustor exit. Furthermore, two different spanwise temperature profiles, one uniform as baseline and one asymmetric profile extracted at the combustor exit from the public literature, are set at the inlet. To adequately resolve the end-wall boundary layers and the mid-span section of the vane in the spanwise direction, as well as the incoming turbulence, the total number of grid points for the simulations is 1.3 billion.

The high-fidelity data generated by the present cases are analyzed to investigate the end-wall secondary features, showing that vortical structures form near the leading edge of the blade include pressure-side and suction-side legs. While the end-wall vortical structures show no obvious effects on the time-averaged behavior of the pressure-side blade boundary layer, the suction-side structures induce counter rotating vortical structures and trigger rapid transition in the end-wall boundary layers. Furthermore, the cases with different inlet temperature profiles are directly compared, and the effects of the inflow on the aerothermal performance of the HPT blade are discussed in detail. Based on the recently proposed entropy loss analysis (Zhao and Sandberg, GT2019-90126), we have been able to quantitatively analyze the effects of the secondary flow features and the inlet temperature distribution, indicating that both the secondary vortical structures and the viscous dissipation in the end-wall turbulent boundary layers contribute significantly to the total loss of the turbine.