The Interaction Between Horseshoe Vortex and Longitudinal Vortices From the Vortex Generators

A horseshoe vortex at the blade-endwall junction introduces the reduction of turbine blade performance due to the three dimensional separation near the stagnation point of the blade and the interaction of the two legs of the horseshoe vortex in the turbine cascade passage. In order to simulate the interaction of the leg vortices in the passage, a pair of vortex generators which produces the longitudinal vortices from the tip of the generator wings is installed upstream of the blade. The experiments are made under the different configuration of the longitudinal vortex generators. NACA 0024 airfoil at zero angle of attack is used as the blade in the wind tunnel where the undisturbed momentum thickness Reynolds number is 1700. The detailed measurements on the three-components of time-averaged and fluctuated velocities are conducted by a small size of rotating X-probe hot-wire anemometer with a miniature stepping motor at the prong. The location of the leg of the horseshoe vortex can be controlled by changing the spacing of the longitudinal vortex generators. The strong dependence of the spacing of the longitudinal vortex generators on the profiles of Reynolds stress and the temporal velocity is clarified.