Optimization of the Performance of Micro Hydro-Turbines for Electricity Generation

Abstract

Rural electrification has long been the most important topic on the development agenda of many countries. The needs for power supplies to rural areas increased significantly in the past decades. Extending electricity grids to rural areas is of a very high initial cost and is not viable economically. Micro hydroelectric power plants provide a good economical solution, which is also environmentally very friendly. The current study concentrates on selecting and optimizing a suitable cross-flow micro-turbine to be used in micro hydroelectric power plants. Cross-flow turbines are in general of simple structure, low cost, easy to fabricate and of modest efficiency. The main purpose of the present work is to optimize the performance of a selected turbine by establishing the optimal turbine’s design parameters. A complete analysis of the internal flow, which is of turbulent, two-phase and three dimensional in nature, was undertaken by simulating it using various CFD simulation codes. This study reports on the flow simulation using ANSYS CFX with a two-phase flow model, water-air free surface model and shear stress transport (SST) turbulence model. Prediction velocity and pressure fields of inside the turbine are, subsequently, used to characterize the turbine performance for different geometric parameters including the number of runner blades, the angle of attack, the ratio of inner to outer diameter, the nozzle profile, the blade profile, the nozzle throat width, the nozzle to runner blades width and the runner blades width to outer runner diameter. The results revealed the highly complex nature of the flow and provided a very good insight to the flow structure and performance optimization parameters.