Optimization of diffuser geometry for an horizontal axis shrouded hydro turbine

The present thesis work concerns the optimization of the shroud of an horizontal axis hydro turbine (HAHT). The main aim is to improve the hydro-turbine efficiency by designing a new shroud airfoil through an optimization process that maximize, as objective function, the power coefficient. The optimization process was carried out by MATLAB©on the supercomputing infrastructure SCoPE of the University of Naples. Results are obtained with CFD calculations, namely by STARCCM+ for an axisymmetric model, taking advantage of the symmetry of the problem, to minimize the computational time; in addition the HAHT is simulated with an actuator disk that gave reliable results in good agreement with previous works, developed with different software, and with experimental results. The original airfoil was designed for high-lift regimes, so it already gave excellent performance in these kind of applications. For that reason, was not expected a very high increase of the power coefficient. Nevertheless the optimization process results into a power coefficient increase of 5.2%, with respect to the original airfoil.