An Experimental Assessment of the Influence of Downstream Conditions on the Performance of a Transonic Turbine Nozzle of High Turning

The present work was conducted to extend information derived in a previous study where it was found that the performance of a transonic turbine nozzle of high turning angle was significantly affected by the design and operation of the downstream rotor and the detailed characteristics of the nozzle flow field. Measurements obtained in an operating stage environment were compared with information from simplified test arrangements. In particular, it was possible to make direct comparisons of static pressure distributions at the vane root as affected by downstream conditions. Detailed exit flow surveys indicated areas susceptible to the influence of rotor presence. Probe interaction effects also were assessed in a special series of tests conducted over a representative range of Mach numbers. Finally, experiments were performed with a perforated plate simulating rotor presence, in an attempt to determine the limitations of such simplified test arrangements in the generation of pertinent data. The results shed further light on a complex subject, and have been aimed at practical validation of test arrangements and techniques.