Shock Boundary Layer Interaction on High Turning Transonic Turbine Cascades

In recent years, the increase in turbine entry temperature, coupled with the capability of higher blade speeds, has led to greater interest in the high work capacity single-stage transonic high pressure turbine. However, the transonic turbine has a performance penalty compared with an equivalent subsonic unit due mainly to shock induced losses. A cascade investigation into the influence of supersonic shocks on turbine blade performance is reported. Two different rotor profiles designed for the same duty were tested in the rectilinear cascade wind tunnel at DFVLR-AVA Goettingen. The results indicate the sensitivity of the cascade performance to shock boundary layer interaction. The importance of Schlieren optics flow visualization (including high-speed film to show the unsteady behavior of the flow) in evaluating the results is discussed.