AAE 415 – Aerodynamic Design

Final Project Presentation

Large Horizontal-Axis Wind Turbine Design

Ted LightJeff Robinson

December 13, 2003

Outline

• Background– Wind Energy & History– Types of Wind Turbines– Wind Turbine Aerodynamics

• Design Process– Starting Point and Analysis Method

• Results

Wind Energy & History

• Wind energy has been used for thousands of years, for sailing, pumping water, grinding grain, etc.

• In the early 1900s, wind turbines were used to produce direct electric current to small areas

• Oil Crisis of 1970s renewed interest in wind turbines as a cheap, clean, unlimited source of energy

Types of Wind Turbines

“Darrius” Vertical Axis Wind Turbine

Large Horizontal Axis Wind Turbine

Traditional Windmill

Airfoil Aerodynamics

Wind = V0

Rotation = r *

Relative Wind = W

• Wind Speed and Turbine Rotation must be combined to find total velocity that airfoil sections “see”

Desired Airfoil Qualities

For a fixed-pitch, constant speed machine, recommended airfoil qualities at 0.75R are:

– High L/D

– Low clmax near tip reduces tendency to overpower generator in high wind speeds

– Insensitive to surface roughness (bugs, birds, bullets)

Design Process

• CMARC used to analyze designs

• Existing wind turbine with known geometry and performance modeled for baseline comparison

• Assumed constant velocity generator(Power) = (Moment)*(Rotation Rate)

• Variation and Analysis of Designs– Geometric parameters modified

Analysis Strategy

• Start with an existing wind turbine, then modify its geometry

• Geometry varied– Airfoil section– Twist distribution– Chord distribution

• Rotational rate, number of blades and span were held constant

Mod-2 Wind Turbine

• Manufactured by Boeing in late 1970s• Development sponsored by NASA

Mod-2 Wind Turbine Specifications

3.45 m 1.43 m

13.7 m

45.7 m

• Diameter = 91.4 m• No. of Blades = 2• Average Wind Speed = 12.5 m/s• Rotation Rate = 17.5 rpm• Airfoil: NACA 23024• Power Output = 2.5 MW

CMARC Inputs

• Rotation rate about x-axis set to that of Mod-2 wind turbine (17.5 rpm)– Many wind turbines are “constant speed”

• Wind Speed set to local average wind speed for Mod-2 (12.5 m/s)

• Baseline geometry emulated Mod-2 geometry, then varied

Results

r/R (1) (2) (3)0 15 14 10

0.25 11.4 11.4 80.5 5.7 7 6

0.75 3.8 3.8 41 2.85 2.85 2

Chord Changesr/R (1) (2) (3)0 6.1 6.0 5.5

0.25 66.7 27.8 83.50.5 83.4 49.5 890.75 93.8 71.3 90

1 111.6 93.0 92

Twist Changes (values in deg from wind axis)

Mod-2 Baseline Model 5816 ---

Mod-A Airfoil Changed to NACA 651-012 5516 -12%Mod-B Airfoil Changed to NACA 65-410 6179 15%Mod-C Airfoil Changed to Althaus AH 93-W-145 2551 -131%Mod-D Chord Change (1) from Mod-B with no sweep 8914 124%Mod-E Chord Change (2) from Mod-B with no sweep 8442 105%Mod-F Chord Change (3) from Mod-B with no sweep 7872 82%Mod-G Chord Change (3) from Mod-B with sweep 9380 143%Mod-H Twist Change (1) from Mod-G 10367 182%Mod-I Twist Change (2) from Mod-G 7849 81%Mod-J Twist Change (3) from Mod-G 7735 77%

Mod-2 Rating Published Power Rating 2500

Model # DescriptionPower (kW)

D from

Baseline

Results

Leading Edge

Root Section

Blade Tip

Airfoil NACA 65-410

r/R Chord (m) Twist (deg)0 10 6.1

0.25 8 66.70.5 6 83.4

0.75 4 93.81 2 111.6

Cp Distribution

Wake

for

Best

Blade

Results

Questions?