Feasibility study for performance prediction of circumferentially compound-stage model turbines

A concept for reducing the testing time of turbine-stage families is propos ed and its feasibility is investigated using computational fluid dynamics ( CFD). A compound stage is used, whose blading around the circumference vari es sectorwise, each sector containing a sequence of equal blades that are d ifferent from the blades in the neighboring sectors. The example chosen inv olves three blade types in the stator and rotor, realizing temporarily nine different stage configurations during a rotor revolution. The application of fast-response flow-measuring techniques is required fur such configurati ons because global measurements of mass flow and torque are not relevant. T he CFD study in a generic subsonic research turbine stage and the subsequen t performance analysis are aimed at showing that the time-dependent short-l ived flowfields in the compound stage are representative of flowfields obta ined in stages with equivalent but circumferentially uniform bladings. A tw o-dimensional unsteady Euler solver is used to predict the full annulus tim e-dependent flowfield within the compound- and uniform-stage. The time-aver age of the unsteady results are fed into loss correlations leading to perfo rmance maps for the nine stage configurations in the compound stage. The co mparison of the computed compound stage results with the uniform stage sugg ests that this concept for assessing the performance of subsonic turbine st ages is basically feasible. This opens up the prospect fur time-resolving q uid flow measuring systems to be successfully applied in such configuration for rapid stage prototyping.