Aerodynamic Performance of Two Isolated Turbine Stators in Transonic Annular Cascade Flow

The objectives of the present work are to investigate experimentally the steady aerodynamic characteristics of two isolated turbine stators and the development of the wakes at transonic flow conditions in an annular turbine facility. The steady three-dimensional flow field was measured at several axial downstream positions and three radial positions using a three-dimensional Laser-Two-Focus anemometer and a total pressure probe. Steady vane surface pressure distributions were recorded on the vane surfaces. A trailing edge shock propagating in the stator downstream flow field was found to have a significant influence on the volocity and turbulence intensity distribution. In the wake strong radial velocity components were obtained. Close to the trailing edge they are directed towards the hub, further downstream the flow is directed towards the tip. At midspan the experimental vane surface data and wake flow data are compared with predictions from two different numerical models: Firstly a 2D/Q3D code solving the viscous terms only in the boundary layer region of the vanes (k-1 turbulence model) and elsewhere the Euler equations, secondly a fully viscous 3D code using a Baldwin-Lomax type turbulence model. Fairly good agreement between numerical results and experimental data were achieved. Differences, which are mainly observed in the wake flow predictions, are assumed to be due to turbulence modeling and a possible grid resolution influence. Furthermore, three dimensional flow contributions were observed in the 3D predictions, especially in the wake region, which could partly lead to the differences between VOLSOL and UNSFLO results. Different trends for the 3D effects have been found in the experiments and for VOLSOL. The data will serve as part of a database for further experimental and numerical investigations of stator-rotor interactions in a turbine configuration. It is assumed that the presented data describe key parameters determining the forced response of a downstream rotor blade row