Parametric characterization of an experimental vertical axis hydro turbine
The current research focuses on the design, fabrication, and testing of an experimental vertical axis tidal current turbine model to obtain first hand experimental data for use in validating numerical codes. In addition to obtaining repeatable experimental results using an entirely new system developed for the UBC towing tank, a parametric study was performed examining the effects of parasitic drag, tip losses, angle of attack, cambered blades, and shaft fairing on a free-stream device. The
... eam device. The impacts on overall efficiency of each characteristic are quantified, leading to a prediction for the maximum efficiency of a free-stream device in the absence of losses. Upon the application of a venturi-style duct, significant gains were demonstrated in the shaft power acquired, as well as in the reduction of torque fluctuations. Application of downstream deflectors provided a further decrease in torque fluctuations with minimal decrease in efficiency, which is significant for structural considerations. A maximum Ck value of 0.473 was obtained for the ducted device compared to 0.272 for the free-stream case; however, the power produced was 12% less than what may be expected from a freestream rotor of cross-sectional area equivalent to the duct capture area. An investigation into drag characteristics of a free-stream device further quantified the drag coefficient that may be expected, as well as the fluctuations of forces in parallel with the free-stream flow. Experimental results were then compared with a commercial RANS solver CFD model from a parallel study. This validation will enable further numerical refinement of the optimum tip-speed ratio and solidity values identified in previous research, as well as further advancements into angle of attack, airfoil profile, and ducting configurations. Lastly, a case study was presented using specif'ing a ducted 3.375m x 3.375m rotor operating in Quatsino Narrows on Vancouver Island capable of powering approximately 17 homes.