Investigation of duct augmented system effect on the overall performance of straight blade Darrieus hydrokinetic turbine

Power generation utilizing the kinetic energy of river flow, tidal, and ocean currents have encouraged the use of Darrieus turbines. However, the low power coefficient, poor self-starting characteristics, and lack of structural analysis have limited their usage. This study, as such, investigates the effect of a ducted augmented system on a Straight Blade Darrieus Hydrokinetic Turbine (SBDHT) to analyze performance, fluid loads, and stress-induced. A one-way Fluid-Structure Interaction (FSI) analysis followed the transfer of fluid forces to the structural module. Real-time hydraulic load and stress were computed and compared for ducted and non-ducted turbines. Computational Fluid Dynamic (CFD) analysis was performed to solve Reynolds Average Navier Stokes (RANS) equations, while turbulences were modeled using k - omega Shear Stress Transport (SST) model. CFD simulation revealed that, for the range of free stream velocity values, the duct augmentation system showed an increase in power production by 112% as compared to non-ducted turbines. The results also reveal that the ducted turbine will experience two-times the hydraulic loads in contrast to non-ducted turbines. Further, induced stress estimation revealed that 178.5 MPa and 94.68 MPa stresses were induced on the ducted and non-ducted turbine, respectively. The stress analysis result showed that maximum stresses occur within the turbine arms and at the joint between shaft and arms. It is, therefore, concluded that the ducted turbine approximately generates double power; however, it also experiences nearly twice stresses compared to the non-ducted turbine, which shall although increase the material cost of the turbine. This study, therefore, recommends that the duct augmentation system should be preferred choice while carefully designing such a system. (c) 2020 Elsevier Ltd. All rights reserved.