Numerical investigation of the flow in a modified Bánki turbine with nozzle foreseen with guide vanes

This paper presents results of a study aimed at verifying whether the usage of a cascade of guide vanes inside the nozzle of a Bánki turbine could improve the turbine performance. Bánki turbines are small cross-flow water turbines used to harvest renewable energy, usually in a range from a few kilowatts to a few hundred kilowatts. First, an existing turbine with classical nozzle was experimentally and numerically investigated to provide a basis for comparison. A mesh sensitivity analysis was performed to find the most appropriate mesh parameters in terms of accuracy and computational resources. After choosing the mesh, the numerical results were validated against experimental data. Second, the turbine with the nozzle modified to accommodate a cascade of guide vanes was numerically investigated. Comparisons of the results obtained on the two nozzle geometries show that the turbine with nozzle foreseen with guide vanes performs clearly better than the classical turbine. The guide vanes assure absolute velocity angles that are closer to the design value. The moment delivered by the modified turbine is significantly higher than that of the classical turbine. Hence, the usage of a nozzle with guide vanes is expected to provide a higher turbine efficiency.