Study of the effect of the geometrical parameters of the runner and operation conditions on performance and flow characteristics in a cross flow turbine

Abstract

Due to technological development, massive use of technology, and accelerated population growth in some regions of the planet, the use of renewable energy sources is important to match the increasing electric energy demand -- Hydropower is an important source of renewable energy around the world, due to its simple but efficient way to provide clean electricity generation -- Currently, the cross flow turbine also known as Banki-Turbine has been increasingly used in many places around the world due to its simple structure, modest efficiency and its good performance in small and low head hydroelectric applications -- It is presumed that the massive utilization of this turbines has been limited due to its low efficiency compared to other turbines with efficiencies near to 90% -- Improving this turbine efficiency would make it more attractive and competitive -- This can be achieved by means of studying the turbine operation and determining the most significant parameters in its performance -- Therefore, the interest of this work is to investigate the performance of the cross flow turbine and the flow characteristics through the turbine -- Two kind of analysis are performed in this work -- The objective of the first analysis is to perform experimental tests of some cross flow turbine prototypes under different operating conditions, and determine its performance -- Due to the differences in the geometrical parameters of the runner on every prototype, an extensive work of design, manufacture and assemble was required for the execution of the experiments in order to obtain satisfactory results -- In the second analysis, CFD simulations of the prototypes are performed with the objective of visualizing the flow through the turbine -- Results show that the turbines with the geometrical parameters selected have a poor performance (approx 50%) under the operating conditions tested -- The prototypes with the best performance are those where the nozzle leads the water to a well defined cross flow in the runner, and the water absolute velocity when entering the runner first and second stage corresponds well to the blade angles -- The prototypes tested show a disordered flow pattern through the runner with big recirculation zones and poorly correspondence with the water velocity vectors and the blade angles, which increases losses and leads to lower efficiencies