The small hydroelectric power plants (SHPP) are implemented in non-interconnected zones (NIZ) of developing countries. In which, the provision of electrical energy from the national interconnected system is not economically feasible. Therefore, in the literature, hydroelectric generation technologies have been implemented taking advantage of the energy available in the rivers. One of these technologies is the Michell-Banki type cross-flow turbines (MBT), which, despite having lower efficiencies than turbines such as Pelton and Francis, maintain their efficiency although fluctuations in site conditions. For this reason, different studies have been made to increase the efficiency of the MBT by making geometric modifications to both the nozzle and the rotor.
The purpose of this study is to determine numerically the effect of the geometry of the blades that form the runner on the efficiency of Michell-Banki Turbine (MBT). For this, two (2) geometries were studied corresponding to a circular sector of a standard tubular profile and an airfoil NACA 6512 modified in curvature profile and chord length, according to the profile of the standard tubular blade. For this study, transient simulations for multiphase water-air flow were implemented using a k-ε turbulence model in the Ansys 2020R1® CFX software. The two (2) turbine models were configured to the same hydraulic conditions of head and volumetric flow corresponding to 0.5 m and 16.27 L/s, respectively. Variations in rotational speed were configured between 100 and 200 RPM with 20 RPM steps. It was found that using the modified 6512 hydrodynamic profile, at 140 RPM increased efficiency by 6 %, compared to the conventional tubular type blade geometry
The aim of this study is to validate, by means of CFD simulation, the effectiveness of a new design methodology formed of a set of updated equations, which allows the design of each of the MBT components to improve its efficiency. In this study, a rigorous investigation of t he MBT literature was carried out, where the most influential design paramet ers and equations in maximum efficiency were determined. Finally, the design of the MBT is carried out with the most relevant equations found in the literature and the design of the MBT is validated by fluid-dynami c tests. It is concluded that the proposed methodology for the design of the MBT can reach efficiencies up to 83 %, which is satisfactory to s ol ve the lack of complete design methods for the sizing of the different components of the MBT (nozzle, runner and housing), according to the flow conditions of the installation site.
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