An Empirical Study into the Power Dynamics of a

Standard Wind Turbine Model Subject to Various

Rotor-Blade Angle Tilt Offsets

Introduction• Lift production is highest on the outer section of the wind turbine blade (Figure 1)

• Goal is to analyze the torque, rotational speed, efficiency, and power output of wind turbine with the turbine blades tilted over a range of offset angles. (Refer to Figure 2)

• We plan to create the following angular offset rotor parts (10 total) : 0°, 0° (2 blades for experimental control part) +4°, - 4°, +7°, - 7°, +10°, - 10°, +30°, - 30°.

- Tilt+ Tilt 0 Tilt

Figure 1: Lift Production vs. blade section Figure 2: Sample of Different Tilt Angles

Turbine Blade Design and Analysis Tools

Design:

Analysis:

Constant Variables in Blade Design

Constant Rotor

Swept AreaConstant Blade Pitch Angle

Blade Pitch

Angle ≈ 22.00°

Vertical Reference Plane(0° rotational offset)

Approval For 3D Printing of Ten Blades

Example Blade: -7° Blade Rotational Offset From Vertical Reference Plane

Rotor Axis of Rotation(Rotor Hub, connects to generator-

nacel testing fixture)

-7° Rotational Rotor Blade Offset Angle -Please Note:

• We wish to 3D-print 10 rotor parts

total (made with two 16” x 14” 3D-

printer trays, approximately 10-15

hours of manufacturing time).

• Each rotor part will be 6 inches in

outer diameter.

• Parts will be made from polycarbonate

(for durability in wind tunnel).

• 10 rotor parts can fit on each 3D-

printer 16” x 14” tray.

• We plan to create the following

angular offset rotor parts (10 total) :

0° x 2 (experimental control part)

+4°, - 4°, +7°, - 7°, +10°, - 10°,

+30°, - 30°.

Quantitative Single Rotor-Part Reference

Metrics (from Solidworks):

1. Polycarb Density = 0.04 pounds per cubic inch

2. Total Mass = 0.01 lbm/ per rotor part

3. Total Volume = 0.26 in^3/ per rotor part

4. Total Surface area = 8.76 in^2 / per rotor part

5. $20.00 Printing Price per cubit inch.

10 rotor parts ≈ 2.6 cubic inches total ≈ $50

3D Printing Process

• ≈ $ 50.00 to print 10 parts in polycarbonate material.

• 10-15 hour printing time (overnight).

Placement on 14’’X16’’ 3D printer

Tray

ASU’s Fortus 400MC 3D

Printer

Physical Analysis Set-Up

Wind Turbine

Blades

IR Sensor to

measure angular

velocity

Electric

Generator

Electrical

Output to

Multi-Meter

Angular

Velocity Data

Output to

DAQ

IR Sensor Support

(Adjustable to multiple

blade angles)

Wind Tunnel Testing Variations

(10 Rotors w/ Angles: 2x 0o, ±4o, ±7o, ±10o, ±30o) x

(4 Wind Speeds: 7 m/s, 10 m/s, 12 m/s, 17 m/s) x

(2 sets of tests: Open Circuit and Closed Circuit)

= 80 wind tunnel tests

Constants

Ambient Temperature and Pressure

Resistance

Rotor Swept Area

Results

Maximum Voltage Produced

Angular Velocity

Open Circuit Testing Procedures1. Set rotor in place

2. Ramp up to maximum testing speed (17 m/s)

3. Record voltage and angular frequency graph at each

wind speed

4. Test through all 4 wind speeds

5. Repeat for the remaining 9 rotors

Closed Circuit Testing Procedures1. Setup the resistor to create a closed circuit

2. Set rotor in place

3. Ramp up to maximum testing speed (17 m/s)

4. Record voltage and angular frequency graph at each

wind speed

5. Test through all 4 wind speeds

6. Repeat for the remaining 9 rotors

Experimental DataConfiguration Power Flow Diagram

Blade

Efficiency &

Losses

Generator

Efficiency &

Losses

Air Velocity, Air

Density Data

Pair = ½*ρ*A*vair^3

Angular Velocity,

Voltage (OC) Data

Pblades = I * α * ω*(Based on Ang. Velocity Data)

Angular Velocity, Voltage

(OC) Data

Pelectrical = V^2/R*(Voltage prop. to Ang.

Velocity Data)

Pair PelectricalPblades

Rotor Angular Velocity vs. Wind Speed

Rotor Angular Velocity Power Functions:ω = A*(vair)^b

Rotor Angular Velocity vs. Tilt Angle Design Curve

Bimodal Curve

(2 Maxima)!

Positive Angle

Maxima ≈ +20°

Negative Angle

Maxima ≈ -25°

Wind Tunnel Simulation Clip

What Did We Determine?

• The tilt angle seems to affect the rotor’s power output (i.e. rotational velocity) along a very

nonlinear, bimodal curve.

o It was visually verified that both the +30° & -30° rotors spun faster than the

baseline 0° rotor.

o Multiple rotors with small offset angles (i.e. +7° to -7°) spun slower than the

extreme angles, and a few rotors (i.e. +4°) resisted rotation all together.

• For maximum power output (i.e. rotational velocity) at a given wind speed and blade

pitch angle (i.e. 22°), one should use a tilt angle at either of the two maxima on the

bimodal design curve chart.

• Physical Reasoning for this Nonlinear Relationship?

• Investigation needs to continue, varying pitch angles and tilt angle together to

better define how the two angles interact and possibly create stall points.

• However, in terms of the conical shape that is formed at the rotor’s extreme

angles: one could speculate either cyclonic (rotating wake) or pressurization

effects (nozzle/diffuser) come into play!

• Possible Explanation: As power imparted by the air to the blades is incoming,

the air forces act over a longer “chord” distance and/or is pressurized leading to

better extraction efficiencies.

QUESTIONS?