Revolutionary Geometries of Mobile Hydrokinetic Turbines for Wind Energy Applications

An abundant source of renewable energy is feasible by harnessing the kinetic energy of moving water using hydrokinetic turbines. The knowledge of wind turbine design, turbomachinery and fluid dynamic principles of incompressible flow can be applied to design traditional and novel geometries of mobile hydrokinetic turbines. A preliminary design is created using the Blade Element Momentum Theory (BEMT) which includes the Prandtl’s correction for tip losses and model corrections. The axial and angular induction factors are calculated iteratively taking into account the coefficient of lift and drag at a certain angle of attack for specific airfoils. Although BEMT does not account for the tip vortices and radial flow induced by the rotation, it provides a good initial geometry. The blade geometry can then be parametrically modified using an in-house 3-D blade geometry generator (3DBGB), and can be analyzed further using a 3-D CFD analysis system. Different configurations such as unshrouded single row, unshrouded counter rotating and shrouded nozzle-rotor-OGV can be explored based on a suitable power requirement. The shrouded design uses a traditional axial turbomachinery approach using 1-D meanline and axisymmetric design-analysis tools (T-AXI suite). Novel geometries with solidity varying spanwise can also be explored to take advantage of the flow across the turbine. A design and analysis system for hydrokinetic turbines is demonstrated. The system is linked to an optimizer to obtain blade shapes with maximum efficiency. A counter rotating design is explored and an optimum design with increased efficiency is obtained. A comparative study of the axial gap between the rotors in a counter rotating system is also presented to show its effect on the power coefficient. The turbine blade designs presented will revolutionize wind energy harness technology.