Hydrodynamic Design and Numerical Simulation of a Very Low Head Axial Turbine (VLH)

Small scale hydraulic power plants equipped with very low head (VLH) axial turbines can be considered as a novel approach to extract energy from rivers and canals. In this study, design process and numerical simulation of a prototype of a VLH turbine is done. The selected turbine generates 450 kW power at the head of 2.6 m. In order to generate the turbine geometry using MATLAB and X-Foil, a computational code has been developed. The design process to generate finalized geometrical data of the runner blades contains a primary hydrodynamic design using Euler equation in turbomachinery, a classical approach for axial turbomachinery design and selection of hydrofoils with appropriate lift coefficient. Using the geometry and structured mesh generated by Turbo Grid for discretization of governing equations, the numerical simulation was accomplished by ANSYS CFX. Simulation results of different opening angles of the runner blades are presented for the turbine system including runner and guide vanes. Also, cavitation possibility is studied in various opening angles and discharges. The results demonstrate that the hydraulic efficiency of the VLH turbine is approximately 89% where the opening angle of the runner blades is at the design point. Moreover, cavitation does not occur at the design point. However, at flow rates larger than the nominal flow rate, and at opening angles larger than the design point cavitation at the leading edge is possible