Abstract
A three-dimensional unsteady flow separation in the straight diffuser of a model bulb turbine is investigated using tuft visualizations, unsteady wall pressure sensors, and particle image velocimetry (PIV). Experimental results reveal a link between the flow separation zone extension and the sudden drop in turbine performances. The flow separation zone grows as the flow rate increases past the best efficiency operating point (OP). It starts on the bottom wall and expands azimuthally and upstream. It deviates and perturbs the flow far upstream. Despite high unsteadiness, a global separation streamline pattern composed of a saddle point and a convergence line emerges.
Highlights
Hydroelectricity is one of the most widely used forms of renewable energy
The goals of this study are to understand the sudden drop in turbine performance at overload condition and describe the flow separation linked to this loss in performance
Measurements of the turbines global parameters and diffuser wall pressure are performed on a large range of operating conditions to describe the global repercussion of flow separation on turbine performance
Summary
Hydroelectricity is one of the most widely used forms of renewable energy. Environmental friendliness, high efficiency and flexibility in electric supply are just some advantages of hydroelectricity. The increased trading and cost of energy have pushed the hydropower industry to install hydraulic power plants in low head sites and to operate turbines in a more extended range of conditions. These new situations have led to heightened research efforts to improve low-head hydro turbines. Among the different types of low-head hydro turbines that exist, bulb turbines are well suited and frequently used for heads under 25 m and high flow rates. One important cause of diffuser losses when the turbine is operated in overload conditions is flow separation, which can lead to a significant reduction of the turbine efficiency
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
