12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Large eddy simulations were carried out in order to investigate the influence of unsteady wakes with different profiles on the loss mechanisms of the T106A linear LPT cascade. The upstream bars were set into rotation around their axis, thus generating circulation as well as asymmetrical wake profiles. Two different rotation rates were simulated yielding different wake parameters that were then compared to an actual turbine blade wake pro-file. It has been found that the commonly used non-rotating bars generated wakes several times stronger than that of a blade. Both wakes were able to trigger early boundary layer transition and thus intermittently prevent separation on the suction surface. However, the weaker wakes resulted in a larger and longer-lasting separation bubble. Interestingly, the bigger separation bubble, in combination with the weaker wakes, resulted in an overall lower loss.