CFD approach for analyzing the effects of rotor stator-interaction in a 3MW mixed flow prototype francis turbine

A 3MW prototype Francis turbine is investigated computationally for analyzing the effects of rotor-stator interaction on hydrodynamic parameters of the turbine consequently on performance of the turbine. An unsteady state numerical simulation of flow passing through the entire flow domain including spiral casing with inlet pipe, Stay vanes, guide vanes, runner and draft tube is carried out utilizing commercial CFD code ANSYS CFX 15.0 for 100% load (mass flow rate 7.2 m³/s) and part load of 60% (mass flow rate 4.71 m³/s). A time step of 3° for total time of 15 full rotations of the runner is considered for transient analysis along with the application of robust shear stress transport (SST K-w) turbulence model. Time dependent pressure and torque fluctuations in runner have been determined and a periodical behavior has been observed. For validation of computational results a steady state simulation is carried out for four guide vane openings corresponding to the 60%, 80%, 100% and 120% loads and a fair agreement with experimental results has been obtained. (author)