Performance of modified gravitational water vortex turbine through CFD for hydro power generation on micro-scale

摘要

Gravitational water vortex turbine takes advantage of the formation of an artificially induced gravitational vortex in a free surface tank, known as basin, for the generation of electrical power with low values of hydraulic head and flow rate. Since this emerging and low-cost technology is still evaluated as a viable alternative to produce hydroelectric energy on the micro-scale, the present work determines its performance with modified geometric parameters using Computational Fluid Dynamics (CFD) techniques. CFD analysis was based on a two-phase flow model covering the vortex formation and the vortex-blade interaction to select an efficient geometric configuration of turbine. The results allowed us to visualize the dynamics of the device, as well as to estimate the vortex height and the production of energy, elements that influence, mainly, the tangential and radial components of velocity. The values of efficiency, torque, and revolutions per minute indicate that a radius coefficient C-r = 0.8 generates better energy absorption. This radius affects the structure of the vortex, mainly in the loss of symmetry of air core, but increases the mechanical efficiency of the turbine based on torque generated. Overall, geometric configuration with a pulse radius of 0.2 m and 8 blades showed the best performance with an efficiency of up to 64.23. Additionally, analysis showed that blade submergence between 90 and 95 induces a braking effect on the rear surfaces of the blades and reduces the level of efficiency.