Underwater Turbines

• Question

The primary question being asked in this project was: Can varying the leading edge tubercles of and underwater turbine increase or decrease the overall performance of the turbine as it collects energy from an underwater current? Will changing the size or orientation of the tubercles effect performance, or not?

• Hypothesis

If the tubercles on the leading edge of an underwater turbine's blade are increased in size, then the performance on the turbine in volts will increase.

• Materials

The materials that will be used in the project to construct the turbine include PVC piping, JB weld, brass piping, brass hex bolts, o-rings, lithium grease, an AC generator, and a two part polyeurathane molding kit to made the blades. Light bulbs of varying ohms and some sockets and wiring will be used to make a board on which the loads necessary to test the turbine will be made. And a small towing device connected to a series of pulleys and coated cord will be used to create the towing tank in which the turbine will be tested.

• Procedures

  • 1. Collect materials and transport them to the pool.

    2. Place the towing system so that each towing hub are parallel and on opposite sides on the testing lane.

    3. Attach the control turbine blade to the nacelle and make sure that the towing guides on the turbine are the same length.

    4. Attach the towing systems cables to both towing guides and place the turbine assembly in the water, while holding the towing cable so that it is outside the water.

    5. String the cables around the towing hubs and pull the turbine towards its starting position at the end of the lane, opposite the motor of the towing system.

    6. Make sure the cables are sufficiently tightened.

    7. Attach a voltmeter and apply an initial load to the turbine.

    8. Begin testing by switching the motor to counter clockwise (CCW) and on.

    9. Record the voltages shown on the electronic readout for cataloging and record the blades rotation in the water for later analysis.

    10. End testing at the end of the lane and switch the motor off

    11. Switch the motor in the clockwise (CW) and on again to tow the turbine back.

    12. Check the tension of the cable on the tow again, and retest the turbine blade under the same load four more times for a total of five trials under the initial load.

    13. After five trials under the first load are completed, the load will be changed.

    14. This new load will be tested in five trials by repeating steps 7 – 12. Five total loads will be tested on the control blade.

    15. The control blade will be exchanged for another blade after it has completed testing.

    16. The tubercle blades will be tested under five different loads for five trials each by repeating steps 6 – 15 until every blade has been tested and recorded.

• Data Collection

Data will be collected by measuring voltages as they pass through the light bulbs by using a multimeter. The blades passage through the water will also be recorded to find the tip speed ratio of the specific rotor under varying ohms.

• Calculations

Power in watts can be derived from voltage and load in ohms through Ohm's Law, which states that power equals voltage squared over ohms, or, P=V^2/I.

Tip Speed Ratio is the relationship between the speed at which the blade is spinning at its tip relative to the current's speed. This ratio can be found with the equation that states that rotational speed in radians per second, hertz, is multiplied by radius and divided by the velocity of the current, or, TSP=w*r/V.

• Project in Practice

Below, is a video detailing the project, and showing how it works in practice. Conclusions on the projects findings are still being concluded.