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Kármán Vortex Street Energy Harvester for Picoscale Applications

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Kármán Vortex Street Energy Harvester for Picoscale Applications Kármán Vortex Street Energy Harvester for Picoscale Applications 22 March 2018 Team Members: James Doty Christopher Mayforth Nicholas Pratt Advisor: Professor Brian Savilonis A Major Qualifying Project submitted to the Faculty of WORCESTER POLYTECHNIC INSTITUTE in partial fulfilment of the requirements for the degree of Bachelor of Science This report represents work of WPI undergraduate students submitted to the faculty as evidence of a degree requirement. WPI routinely publishes these reports on its web site without editorial or peer review. For more information about the projects program at WPI, see http://www.wpi.edu/Academics/Projects. Cover Picture Credit: [1] Abstract The Kármán Vortex Street, a phenomenon produced by fluid flow over a bluff body, has the potential to serve as a low-impact, economically viable alternative power source for remote water-based electrical applications. This project focused on creating a self-contained device utilizing thin-film piezoelectric transducers to generate hydropower on a pico-scale level. A system capable of generating specific-frequency vortex streets at certain water velocities was developed with SOLIDWORKS modelling and Flow Simulation software. The final prototype nozzle’s velocity profile was verified through testing to produce a velocity increase from the free stream velocity. Piezoelectric testing resulted in a wide range of measured dominant frequencies, with corresponding average power outputs of up to 100 nanowatts. The output frequencies were inconsistent with predicted values, likely due to an unreliable testing environment and the complexity of the underlying theory. A more stable testing environment, better verification of the nozzle velocity profile, and fine-tuning the piezoelectric circuit would allow for a higher, more consistent power output. 1 Table of Contents Abstract ........................................................................................................................................................1 1. Introduction .............................................................................................................................................7 2. Literature Review ...................................................................................................................................8 2.1 Types of Run-of-River Hydropower .................................................................................................8 2.2 The Kármán Vortex Street ............................................................................................................... 10 2.2.1 Vortex Shedding ............................................................................................................................ 11 2.2.2 Vibrations ...................................................................................................................................... 12 2.2.3 Kármán Vortex street as an energy source .................................................................................... 13 2.3 Past Works ......................................................................................................................................... 13 2.3.1 Eel Harvester Method .................................................................................................................... 13 2.3.2 Oscillating Bluff Method ............................................................................................................... 15 2.3.3 Previous MQP’s ............................................................................................................................. 15 2.4 Piezoelectric Energy Harvesting ..................................................................................................... 16 2.4.1 Piezoelectric Materials .................................................................................................................. 16 2.4.2 How Piezoelectrics Operate ........................................................................................................... 17 2.4.3 Power Output from Piezoelectrics ................................................................................................. 17 3. Kármán Vortex Street Energy Harvester Design ............................................................................ 20 3.1 General Simulation Methods ........................................................................................................... 20 3.1.1 Standard Boundary Conditions ...................................................................................................... 20 3.1.2 Computational Domain .................................................................................................................. 21 3.1.3 Mesh Sizes ..................................................................................................................................... 21 3.2 Oscillating Bluff Body Design ........................................................................................................ 21 3.2.1 Preliminary Design ........................................................................................................................ 21 3.2.2 Preliminary Calculations ............................................................................................................... 23 3.2.3 Preliminary Sketches/Drawings ..................................................................................................... 25 3.2.4 Determining the Aspect Ratio ....................................................................................................... 25 3.2.5 Force Analysis ............................................................................................................................... 27 3.3 Eel Harvester Design ........................................................................................................................ 29 3.3.1 Preliminary Eel Harvester Design ................................................................................................. 29 3.3.2 Preliminary Calculations ............................................................................................................... 30 3.3.3 Preliminary Sketches/Drawings ..................................................................................................... 31 3.3.4 Flow Simulations to Revise Nozzle Design .................................................................................. 33 3.3.5 Determining the Redesigned Nozzle Aspect Ratio........................................................................ 39 3.3.6 Determining the Minimum Bluff Body Diameter ......................................................................... 41 3.3.7 Final Eel Nozzle Design ................................................................................................................ 43 3.4 Bluff Body Mechanism Design ...................................................................................................... 45 4. Nozzle Construction Process ............................................................................................................. 51 5. Testing and Analysis .......................................................................................................................... 53 5.1 Testing Methodology ....................................................................................................................... 53 5.1.1 Building the Testing Rig ................................................................................................................ 54 2 5.2 Nozzle Velocity Profile .................................................................................................................... 54 5.2.1 Pressure Transducers and Calibration ........................................................................................... 55 5.2.2 Pressure Transducer Calibration Results ....................................................................................... 55 5.2.3 Velocity Profile Testing Initial Results ......................................................................................... 57 5.2.4 Recalibration and Final Velocity Profile Results .......................................................................... 59 5.3 Piezoelectric Testing ........................................................................................................................ 60 5.3.1 Piezoelectric Testing Power Output Results .................................................................................. 60 5.3.2 Piezoelectric Testing Frequency Results ....................................................................................... 61 5.4 Results Discussion ............................................................................................................................ 63 5.4.1 Power Output ................................................................................................................................. 63 5.4.2 Frequency ...................................................................................................................................... 63 6. Conclusions .......................................................................................................................................... 65 6.1 Testing ................................................................................................................................................ 65 6.2 Theory ...............................................................................................................................................
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