Resumo:
This work presents design guidelines to eliminate unwanted hydrodynamic effects on diffuser augmented hydrokinetic and wind turbines. The occurrence of boundary layer separation from the solid surfaces situated inside the diffuser tends to be detrimental for performance, frequently harming the mass flow capture and, consequently, decreasing the machine’s capacity to generate power.
A set of studies involving the design and CFD simulation of diffuser-augmented turbines is presented. In these studies, the conditions of occurrence of these unwanted hydrodynamic effects, their impact on performance from the quantitative point of view and design strategies to avoid them are discussed.
The results show that the harmful hydrodynamic phenomena are sensitive to rotor loading. Besides, the studies show that a moderate tip clearance, in conjunction with a rotor geometry with an unloaded blade root and a specific loading condition for the rotor are beneficial to the performance of diffuser augmented hydrokinetic turbines.
Lastly, guidelines for the design of diffuser-augmented turbines are presented with the objective to guide the designer towards a high standard configuration.
