Flow separation control by using bowed blade in highly loaded turbine cascades

Due to the serious flow separations and centralized vortices, there are high secondary losses in highly loaded turbines. It is imperative to find measures to control the flow separation and vortices hence improve the turbine performance. This paper reports our recent progress on flow separation and vortices control in highly loaded turbine cascades by using bowed blades. Two sets of highly loaded turbine cascades with the turning angles of 113A degrees and 160A degrees, and each with 7 bowed blade angles 0A degrees (straight), +/- 10A degrees, +/- 20A degrees and +/- 30A degrees were experimentally investigated. Both internal flow field measurement and flow visualization on the blade surfaces were conducted, and the effects of blade bowing on the flow topology, distribution of vorticity and the flow energy loss were discussed. The results show that, for the cascade with the turning angle of 113A degrees, the appropriately positive bow angle could reduce the flow energy loss; whereas for the cascade with the turning angle of 160A degrees, the well selected negative bow angle can give the better aerodynamic performance.