Investigation of the effect of gaps between the blades of open flume Pico hydro turbine runners

Abstract

This study will analyze the impact of gap size in two different runners called runner A (five blades) and B (six blades) to provides recommendations in design and manufacture of open flume turbine runners so that maximize the conversion of kinetic and potential energy. There are three methods was used to investigate its: analytical method is used to design the turbine; experimental to determine the actual turbine performance; computational fluid dynamics (CFD) to study the physical phenomena and re-check the velocity triangle on the runner to validate the design and manufacturing process. Using the results obtained, gaps between the blades can alter the velocity vector on the outlet and unbalance the rotation of runner; this imbalance could cause cavitation. Then, the decreasing torque is assumed because water pressure in the draft tube is similar to atmospheric pressure. Two conditions must be satisfied to maximize the performance of the turbine: swirling flow is required after the water flows past the runner in order to minimize the radial velocity on the outlet so that the draft tube can function properly; the dimensions of the blade must be carefully selected to avoid the formation of gaps between the blades.