Report and Presentation work

Today the group met to continue editing and improving the Final Report and Presentation for the project. Sections of the report and slideshow were distributed among group members to focus on individually.

We discussed the adjustments made to the PVC end capping to hold in place the rod connecting the gear system to the motor, as mentioned in the previous post.  For testing, a small piece of scrap metal was duct taped into position above the rod's intended resting location to prevent the rod from moving upwards as the gear system turned, keeping it locked in its proper horizontal location. Should the turbine require any further testing, this apparatus will be more firmly put into place using paperclip attachments as we have with other rods.

We will meet tomorrow to compile a final presentation slideshow of our individual efforts and to practice our presentation several times to be sure we can cover the necessary details in the allotted timeframe. The group's progression through the project is in line with the original projected timeline, as planned.

Today's Testing

Today we completed our final test of our wind turbine. Our turbine performed well at all wind speeds, and at each of the three gear ratios. After today's testing we noticed that the back panel of the turbine would have to be retrofitted with metal supports around each shaft hole. The reason for this modification is to prevent the degradation of the plastic as the shafts spin at the higher speeds. As we were testing without this modification today the holes widened with time causing the shafts to jump and a large amount of gear slip to occur. As of now we have made necessary fixes and this problem has been resolved. We also came to the conclusion today that our power output is severely limited by our small DC motor and not the turbine design itself. The turbine spins well at all speeds and can handle the maximum wind speed at all gear ratios. If a higher quality generator were hooked up to the turbine we are confident that we would see a significant increase in the power output. A video of today's testing can be viewed by clicking the link below.

Testing video from 6-3-13

Final Assembly

The final assembly in working condition with a fresh coat of paint.

Wind Blade design

For the blade design, we used one of the links (see below [1]) from our section BB Learn page for insight into the factors that make up the blades. It explains that an attack angle of 15 degrees is ideal for the blade system, because any steeper of an angle begins to induce stalling (3). This seemed to agree with a few other sources on the internet, therefore we determined that 15 degrees is the best choice for a symmetrical blade design. The formula B=(80/λ²) was used to find the optimum number of blades, B, where λ is the tip to speed ratio (10). This reference states that this ratio should be between 5 and 8; in our design we used a ratio of λ=5. The resulting value of B was 3.2, which was rounded down to 3 blades for our system.

[1]    http://www.scoraigwind.com/wpNotes/bladeDesign.pdf

3-Blade Design in Creo Parametric

Materials Purchased

While purchasing the materials, we realized the 6 inch tube that we previously planned to use for the gear system housing would have been too big and cumbersome to fit in the wind tunnel, so we decided instead to use the 4 inch tube.  All that is needed are the gears and fan blades and we can begin assembling the model.

Week 5: Thursday Lab Meeting

This week the group further discussed how we would like to build the gear system and its housing. We decided that the gear shafts must be made of metal and talked about different possibilities for the shape of these shafts. For the housing of the gear system we settled on using 6" of PVC piping and end caps. This will be easy to drill through and set up the gear system inside, while creating other openings to keep as aerodynamic as possible. We hope to have these pieces by next lab.

Investigating Gear Ratios

The group has been hard at work the last two weeks on the gear system and fan blade designs.

Last week in lab on Thursday, the group began investigating the math behind gear ratios and how sets of gears relate to each other when connected. Gear or speed ratio is the angular velocity of the input gear over the angular velocity of the output gear. It can also be expressed as the number of teeth on the input gear over the number of teeth on the output gear.

The group decided on the gear ratios for each of the three speeds at which the gears will function and downloaded CAD drawings of each of these gears to assemble.

The fan blade design continues to be adjusted and improved as more research is conducted on how best to shape them.

Some photos of the group members at work:

Kory assembles gears on a gear shaft

Sam C. experiments with gear spacing along multiple shafts

Sam V. tweaks the fan blade design as the group develops new ideas