Passive Flow Control in Vertical Axis Wind Turbines

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PI: Evans, SimonProposal Number: 1336474Institution: Worcester Polytechnic InstituteTitle: Passive Flow Control in Vertical Axis Wind TurbinesThis project will investigate the use of passive flow control as a way to improve the performance of vertical axis wind turbines (VAWTs), by preventing dynamic stall at low tip-speed ratios. The performance improvements that the scheme enables in the wind turbine will also be assessed. The research will include numerical optimization of a vertical axis wind turbine blade through one full revolution, at a tip speed ratio for which the blade stalls. This optimization will identify a blade design and pitch offset to maximize the performance of a passive flow control scheme while minimizing the impact of the scheme on blade performance when not stalled. This flow control scheme consists of vortex generator jets driven by the pressure difference existing across the blade at stall conditions. The optimization will be performed with a routine in MATLAB that passes variables to the Unsteady RANS solver, FLUENT. The blade design resulting from the optimization will be used in a parametric study conducted experimentally using a pitching airfoil in a wind tunnel, with the passive flow control scheme implemented. Parameters such as jet hole size and injection direction will be varied in this parametric study. The time-resolved lift and drag determined from measurements taken in the experiments will be used to estimate the improvement in shaft power delivered by the turbine.This research will evaluate an approach to increase the torque and power delivery of vertical axis wind turbines, increasing their efficiency in converting wind energy to shaft power and therefore increasing their potential to contribute significantly to national energy production. VAWTs are seen as particularly attractive for the urban and home power generation markets in which wind conditions are unsteady and wind directions variable. However, low efficiency resulting from dynamic stall has kept adoption rates low. This research will evaluate an approach to improve the efficiency of these turbines, by controlling the dynamic stall at low tip-speed ratios, thereby allowing growth of these markets. This will reduce dependence on the grid by moving energy generation to the point of use, contribute to reducing the country?s reliance on fossil fuels and reduce greenhouse gas emissions by increasing the percentage of power generation by renewable wind energy.This project will utilize WPI?s project-based education to engage and train undergraduates in state-of-the art experimental and computational methods and to supply high-school science teachers with a curriculum unit on wind energy that they can use in the classroom. All WPI undergraduates are required to complete a junior team project, the Interactive Qualifying Project (IQP), and a senior team project, the Major Qualifying Project (MQP). Each is equivalent to three courses. MQP projects will be conducted over 3 years and will support the experimental and computational efforts. IQP projects will be conducted over 2 years and will develop and pilot a curriculum unit on wind energy for implementation in the high-school science curriculum. This curriculum unit will be developed with the support of WPIs unique STEM Education Center and the Worcester Public Schools, to address specific core ideas in the Massachusetts Science Standards, including conversion of energy and energy transfer, the relationship between energy and forces, and renewable energy.