Cosan Daskiran

Computational Study of Multiple Hydrokinetic Turbines: The Effect of Wake

Computational Fluid Dynamics (CFD) simulations have been conducted to investigate the performance of a predetermined propeller-based hydrokinetic turbine design in staggered and non-staggered placements for river applications. Actual turbine models were used instead of low fidelity actuator line or actuator disks for CFD simulations to achieve more reliable results. The k-ω Shear Stress Transport (SST) turbulence model was employed to resolve wall effects on turbine surface and to determine wake interactions behind the turbines. The wake interaction behind the upstream turbine causes significant drop on downstream turbine performance within non-staggered configuration. The upstream turbines in both staggered and non-staggered placement offers the same relative power of 0.96, while the relative power for downstream turbine is 0.98 for staggered installment and 0.16 for inline placement.Copyright

Large Eddy Simulations of Ventilated Micro Hydrokinetic Turbine

Large eddy simulations of pre-designed micro-hydrokinetic turbine were conducted to investigate the oxygen transfer from air to water. Simulations were performed in extreme conditions having a tip-speed ratio of 3.8 that is higher than the tip-speed ratio at turbine’s design point. Air was injected from the turbine hub downstream in axial direction. Both single phase and multiphase simulations were performed to reveal the influence of air admission on the flow structures and the turbine performance. The mixture multiphase model was employed in multiphase simulation. The results indicated that turbine power generation was reduced roughly 10.5% by air admission, however the torque applied on turbine surface in axial direction did not vary significantly by aeration. The aeration assisted in the suppression of vortices within the flow field. The deviation of the power coefficient and the thrust coefficient was reduced roughly 32% through the inclusion of aeration process.Copyright

Design and Characteristics of the Micro-Hydrokinetic Turbine System

Small, hydrokinetic systems generating between 0.5 and 10 kW of power allow for the potential of portable power generation. An optimized propeller turbine approximately 0.6826 m in diameter and a diffuser with an area ratio of 1.31 were used to produce a prototype for preliminary testing. The optimized diffuser augmented hydrokinetic turbine was investigated numerically to predict power and thrust curves for comparison during experimental testing. A gear box with a 10:1 gear ratio was selected for converting torque to angular velocity. A DC permanent magnet generator was selected for mechanical-electrical power conversion. At the ideal generator operating conditions consisting of a shaft rotation rate of 1150 RPM, a voltage of 48 V, and current of approximately 8 A, 375 W of power may be generated at a river flow speed of 1.5 m/s. Numerical predictions coupled with component efficiencies yield a system efficiency of approximately 0.61 before DC/DC conversion and 0.52 after DC/DC conversion.Copyright