Evaluation of Impulse Turbines for a Wave Energy Converter

The extraction of wave energy through self-rectifying air turbine is one of the emerging technologies for oscillating water column (OWC) based wave energy devices. In the present effort, a bi-directional impulse (BDI) turbine is designed and the performance parameters were found numerically and compared with an existing unidirectional impulse (UDI) turbine. A brief analytical formulation through similarity laws, to find a dynamically similar BDI turbine using pressure drop vs flow characteristics, gives the approximate diameter range equivalent to the reference UDI turbine. The results are used to reduce the range of diameters and it is found that the characteristics are matching with the reference UDI turbine. The maximum and minimum diameters among the selected range are considered for detailed computational fluid dynamics (CFD) analysis. These two BDI turbines are modeled and meshed in ICEM CFD 14.5. The commercial CFD code CFX 14.5 is used for the numerical simulations. The Reynolds-averaged Navier-Stokes (RANS) equations with the standard k-ϵ scalable wall function model are solved to obtain the performance parameters. A detailed flow physics of the BDI turbines has also been included.