Numerical investigations on performance improvement of cross flow hydro turbine having guide vane mechanism

Abstract

ABSTRACT Cross-flow turbine is one of the leading turbines to harness the hydropower potential in micro-hydro power schemes. In spite of having a simple structure, low maintenance, and low initial investment, this turbine suffers the problem of low efficiency due to unguided flow in the runner cavity. In the present study, an attempt has been made to enhance the performance of cross-flow turbine by attaching hydrofoils shaped (symmetrical and unsymmetrical) guiding mechanism. The effectiveness of the placement of guide vane was examined numerically in terms of turbine efficiency and flow field distributions. The performance of the modified turbine was compared with the turbine having no guide vane. The position and placement angle of the guide vanes were also investigated to find the suitable position of the guide vane in the runner cavity. The turbine with symmetrical and unsymmetrical guide vane yields its maximum efficiency corresponding to vane angle of 55° and 45°, respectively, placed at the ‘right’ position (toward nozzle) for both types of guide vanes. The maximum efficiency of the turbine was observed as 80.1% and 79.9% corresponding to symmetrical and unsymmetrical guide vanes, respectively. Further, the flow field distribution inside the turbine runner and in the vicinity of the guide vane has been observed. It has been visualized that placement of the guide vane minimizes the water recirculation with the streamlined flow for smooth entry to the second stage of the runner. The reduction in turbulence and vortices generation results in the improvement of turbine efficiency for similar operating conditions.