Unsteady loss in a high pressure turbine stage

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 at all vane and rotor-relative positions over a wide range of radial height. Due to the considerable difficulty of obtaining accurate measurements at engine-representative conditions, these measurements provide a unique set of experimental data. Five distinct flow features have been identified and their effects on the stage efficiency estimated, showing good overall agreement with an independent efficiency measurement. Comparisons with a particular numerical prediction of the flow field, Unstrest, have shown very good agreement in both the flow structure and the entropy generation. Only the rotor dependence of the loss mechanisms is examined here: the vane dependence will be presented in a subsequent paper.