Feasibility Study for Performance Prediction of Circumferentially Compound-Stage Model Turbines

Abstract

Aconcept for reducing the testing timeof turbine-stage families is proposedand its feasibility is investigatedusing computational  uid dynamics (CFD). A compound stage is used, whose blading around the circumference varies sectorwise, each sector containing a sequence of equal blades that are different from the blades in the neighboring sectors. The example chosen involves three blade types in the stator and rotor, realizing temporarily nine different stage conŽ gurations during a rotor revolution. The application of fast-response  ow-measuring techniques is required for such conŽ gurations because globalmeasurements of mass  ow and torque are not relevant. The CFD study in a generic subsonic research turbine stage and the subsequent performance analysis are aimed at showing that the time-dependent short-lived  owŽ elds in the compound stage are representative of  owŽ elds obtained in stages with equivalent but circumferentially uniform bladings. A two-dimensional unsteady Euler solver is used to predict the full annulus time-dependent  owŽ eld within the compoundand uniform-stage. The time-average of the unsteady results are fed into loss correlations leading to performance maps for the nine stage conŽ gurations in the compound stage. The comparison of the computed compound stage results with the uniform stage suggests that this concept for assessing the performance of subsonic turbine stages is basically feasible. This opens up the prospect for time-resolving  uid  ow measuring systems to be successfully applied in such conŽ guration for rapid stage prototyping.