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?
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