Parametric studies of the aerodynamic excitation in high pressure turbines

Numerical and experimental studies are performed on the influence of several key parameters on the aerodynamic exitation of a high-pressure turbine rotor blade row due to the upstream stator row. In order to change the vane passing frequency two stators with similar vane shapes and identical exit Mach number and exit flow angle are used. To be able to separate subsonic and transonic stator induced flow distortions data is recorded at two different flow regimes. The axial gap between stator and rotor is varied as well. Experiments were run in a closed loop high speed annular wind tunnel. Unsteady velocity data were measured with a three-dimensional Laser-Two-Focus anemometer between stator and rotor and downstream of the rotor. The unsteady part of the instantaneous velocity, the gust, is split into streamwise, transverse and radial components and harmonically decomposed. This data is compared to numerical results obtained with a quasi 3D method (UNSFLO) and analysed regarding two aspects: the dependency of the gust on the changed parameters and the impact of the gust on the forcing function (blade excitation pressures)