Unsteady loss in a high pressure turbine stage: Interaction effects

An investigation into the unsteady losses in a high pressure turbine stage has been performed experimentally at engine-representative conditions. This has been done by making time-resolved measurements of entropy at stage exit over all vane and rotor-relative positions over a wide range of radial height. These measurements provide a unique set of experimental data in that this is the first time that a full-field unsteady entropy survey has been attempted in a turbine facility capable of realistic Reynolds and Mach numbers. In a previous paper [Int. J. Heat Fluid Flow 24 (2003) 698] the exit flow of the rotor at one vane relative phase was reported. This allowed the loss associated with rotor flow features such as wakes, tip flows and secondary flows to be determined. The aim of this paper is to investigate the effects of vane-rotor interaction on both the time-mean and time-resolved performance of the stage. In addition to the experimental results, an unsteady Reynolds-averaged Navier-Stokes prediction of the flow field within the stage has been undertaken. Comparison of the experimental measurements with the prediction showed that time-mean efficiencies differ by 1.2%. The experimental results showed an unsteady change in stage efficiency of 1.2% as the rotor moves relative to the upstream vane. This was much higher than the 0.2% change predicted by the unsteady solver.