Investigation of an Annular Cascade of Nozzle Guide Vanes with Air Ejection; Flow Field Mapping with Laser-2-Focus Velocimetry

Abstract

Experiments are carried out in the windtunnel for rotating cascades (RGG) at DLR Goettingen, which belong to the BRITE/ EURAM IMT Area 3 Turbine Project, Package A "Wake-Blade Interference in Transonic HP Turbines" of the European Community. Investigations in the passage and downstream of the annular cascade of nozzle guide vanes are described in this report. This stator of the IMT turbine stage operates in the transonic flow regime, M/2 &#61 1.05, and is supplied with air ejection at the pressure side in the trailing edge area as simulation of internal cooling; the coolant mass flow rate ranges from c/m &#61 0% till 3%. The application at midspan of laser-two-focus velocimetry results in detailed and accurate information on the development of Mach number, flow angle, turbulence intensities and Reynolds shear stress. The mixing process of the jet of ejected air with the main flow is measured by the addition of seeding particles to the coolant and counting the rate of passing particles in the wake. The resulting data base firstly is to be used by the project partners for comparison with their cfd developments and secondly the discrepancies with respect to the experiments on the complete stage will have to be analysed.