Combined Effects of Turbulence Intensity and Periodic Unsteady Wake Flow Condition on Boundary Layer Separation and Re-attachment along the Suction Surface of a Low Pressure Turbine Blade

摘要

The paper experimentally investigates the individual and combined effects of periodic unsteady wake flows and free-stream turbulence intensity (FSTI) on flow separation along the suction surface of a low pressure turbine blade. The experiments were carried out at a Reynolds number of 110,000 based on the suction surface length and the cascade exit velocity. The experimental matrix includes free-stream turbulence intensities of 1.9%, 3.0%, 8.0%, 13.0% and three different unsteady wake frequencies with the steady inlet flow as the reference configuration. Detailed boundary layer measurements are performed along the suction surface of a highly loaded turbine blade with a separation zone. Particular attention is paid to the aerodynamic behavior of the separation zone at different FSTIs at steady and periodic unsteady flow conditions. The objectives of the research are: (a) to quantify the effect of FSTI on the dynamics of the separation bubble at steady inlet flow conditions, and (b) to investigate the combined effects of FSTI and the unsteady wake flow on the behavior of the separation bubble. The experimental investigations were performed on a large scale, subsonic unsteady turbine cascade research facility at the Turbomachinery Performance and Flow Research Laboratory (TPFL) of Texas A&M University.