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

Week 4 Update

This past week we focused on organizing what materials we will need for the gear housing and gear shafts. We realized after a conversation with Deepak, that we could not 3D print these things and they would have to be purchased. So far we are thinking of some kind of preformed plastic casing for the housing, and metal rods (possibly threaded) for the gear shafts. While this is a change in our plan we do not believe it will effect our project timeline.

Wind Blades

Above are some screen shots of a new possible wing based on some general blade research I have conducted. The indentation in the wing is the key to setting the blade at an angle of 17 degrees, which has been shown to be the optimum angle of attack for wind turbines. The actual center of the wind blades is incomplete, as it will include 4 blades, not 2.