1. AERSP 496 (10/10/2017)
Milton Rahman

2. Aero team update
The main objective of the aerodynamics team is to improve upon the blade design from the previous years.
One idea was to design a blade to a tip speed ratio (TSR) of 7 as this is the ideal TSR for large scale blades.
However after some thought and analysis we determined that at a small scale like this, we may end up actually losing power after a TSR of about 4.5.
The goal now is to design blades to a TSR of between 4 and 4.5.

3. How we define a blade’s geometry
Center of rotor
Chord Length
Radius

4. How we define a blade’s geometryX

5. Rick’s Excel code
For the last few years, we have used Rick Auhl’s excel code to design our blades.
Although this code does work and does give us decent blade designs, it isn’t very accurate.
The code also iterates to an ideal axial induction factor of .333 at every point along the blade. In real life, this won’t be the case due to hub and tip losses.
The code also tends to increase the chord at every point along the radius of the blade in order to increase torque and power.
We may start to move away from using the code for design purposes however it is still a great learning tool.

6. X-Turb
We have been using X-Turb to analyze last years blades as a benchmark for improvement.
X-Turb outputs have shown us how well our blades will perform under a number of different conditions of TSR and pitch.
Dr. Schmitz is currently working to update the design function of X-Turb. Once he has completed this, we should be able to input desired TSR, design wind velocity, and desired L/D max and out put a blade geometry.
We are fairly happy with the solidity of the rotor. We are going to probably keep the chord length at each radial position the same.
We will play around with the twist distribution along the radius in order to achieve a maximum L/D.

7. Current Cl vs Cd graph
This is about the area of the Cl vs Cd curve we want every point on the blade to be operated at because it will give us the around the maximum L/D.

8. Future work
Instead of changing the chord lengths (the way the excel code will), we are going to play around with the twist of the current blade design in order to have each radial station of the blade at it’s ideal angle of attack.
For the FX airfoil, the ideal angle of attack at a Reynold’s number of is about 6 or 7 degrees. This angle of attack gives us the maximum L/D. Therefore we would want to design every radial station along the blade that operates at Re to have an angle of attack of 6 or 7 degrees.
More analysis will need to be done on the different Reynolds numbers we operate at in order to determine the ideal angle of attacks at all the other radial stations.
The aero team may begin to use the negative aluminum molds of the blades from last year in order to make some carbon fiber blades.
If we successfully make three carbon fiber blades that well balanced, we will run them in the wind tunnel and compare the performance to the 3-D printed blades.

9. Molds for carbon fiber blades